From a0e4013becb7f7b786a474545335a4c82c12f1af Mon Sep 17 00:00:00 2001 From: matianjun1 Date: Sun, 18 Jun 2017 21:40:30 +0800 Subject: [PATCH 1/4] add exercise with suggestion --- 100 Numpy exercises with suggestion.ipynb | 1709 +++++++++++++++++++++ 100 Numpy exercises with suggestion.md | 445 ++++++ 2 files changed, 2154 insertions(+) create mode 100644 100 Numpy exercises with suggestion.ipynb create mode 100644 100 Numpy exercises with suggestion.md diff --git a/100 Numpy exercises with suggestion.ipynb b/100 Numpy exercises with suggestion.ipynb new file mode 100644 index 0000000..7905b84 --- /dev/null +++ b/100 Numpy exercises with suggestion.ipynb @@ -0,0 +1,1709 @@ +{ + "cells": [ + { + "cell_type": "markdown", + "metadata": {}, + "source": [ + "# 100 numpy exercises with suggestion\n", + "\n", + "This is a collection of exercises that have been collected in the numpy mailing list, on stack overflow and in the numpy documentation. The goal of this collection is to offer a quick reference for both old and new users but also to provide a set of exercices for those who teach.\n", + "\n", + "\n", + "If you find an error or think you've a better way to solve some of them, feel free to open an issue at " + ] + }, + { + "cell_type": "markdown", + "metadata": {}, + "source": [ + "#### 1. Import the numpy package under the name `np` (★☆☆) (suggestion: import … as ..)" + ] + }, + { + "cell_type": "code", + "execution_count": null, + "metadata": { + "collapsed": true + }, + "outputs": [], + "source": [] + }, + { + "cell_type": "markdown", + "metadata": {}, + "source": [ + "#### 2. Print the numpy version and the configuration (★☆☆) (suggestion: np.\\_\\_verison\\_\\_, np.show\\_config)" + ] + }, + { + "cell_type": "code", + "execution_count": null, + "metadata": { + "collapsed": false + }, + "outputs": [], + "source": [] + }, + { + "cell_type": "markdown", + "metadata": {}, + "source": [ + "#### 3. Create a null vector of size 10 (★☆☆) (suggestion: np.zeros)" + ] + }, + { + "cell_type": "code", + "execution_count": null, + "metadata": { + "collapsed": false + }, + "outputs": [], + "source": [] + }, + { + "cell_type": "markdown", + "metadata": {}, + "source": [ + "#### 4. How to find the memory size of any array (★☆☆) (suggestion: size, itemsize)" + ] + }, + { + "cell_type": "code", + "execution_count": null, + "metadata": { + "collapsed": false + }, + "outputs": [], + "source": [] + }, + { + "cell_type": "markdown", + "metadata": {}, + "source": [ + "#### 5. How to get the documentation of the numpy add function from the command line? (★☆☆) (suggestion: np.info)" + ] + }, + { + "cell_type": "code", + "execution_count": null, + "metadata": { + "collapsed": true + }, + "outputs": [], + "source": [] + }, + { + "cell_type": "markdown", + "metadata": {}, + "source": [ + "#### 6. Create a null vector of size 10 but the fifth value which is 1 (★☆☆) (suggestion: array\\[4\\])" + ] + }, + { + "cell_type": "code", + "execution_count": null, + "metadata": { + "collapsed": false + }, + "outputs": [], + "source": [] + }, + { + "cell_type": "markdown", + "metadata": {}, + "source": [ + "#### 7. Create a vector with values ranging from 10 to 49 (★☆☆) (suggestion: np.arange)" + ] + }, + { + "cell_type": "code", + "execution_count": null, + "metadata": { + "collapsed": false + }, + "outputs": [], + "source": [] + }, + { + "cell_type": "markdown", + "metadata": {}, + "source": [ + "#### 8. Reverse a vector (first element becomes last) (★☆☆) (suggestion: array\\[::-1\\])" + ] + }, + { + "cell_type": "code", + "execution_count": null, + "metadata": { + "collapsed": false + }, + "outputs": [], + "source": [] + }, + { + "cell_type": "markdown", + "metadata": {}, + "source": [ + "#### 9. Create a 3x3 matrix with values ranging from 0 to 8 (★☆☆) (suggestion: reshape)" + ] + }, + { + "cell_type": "code", + "execution_count": null, + "metadata": { + "collapsed": false + }, + "outputs": [], + "source": [] + }, + { + "cell_type": "markdown", + "metadata": {}, + "source": [ + "#### 10. Find indices of non-zero elements from \\[1,2,0,0,4,0\\] (★☆☆) (suggestion: np.nonzero)" + ] + }, + { + "cell_type": "code", + "execution_count": null, + "metadata": { + "collapsed": false + }, + "outputs": [], + "source": [] + }, + { + "cell_type": "markdown", + "metadata": {}, + "source": [ + "#### 11. Create a 3x3 identity matrix (★☆☆) (suggestion: np.eye)" + ] + }, + { + "cell_type": "code", + "execution_count": null, + "metadata": { + "collapsed": false + }, + "outputs": [], + "source": [] + }, + { + "cell_type": "markdown", + "metadata": {}, + "source": [ + "#### 12. Create a 3x3x3 array with random values (★☆☆) (suggestion: np.random.random)" + ] + }, + { + "cell_type": "code", + "execution_count": null, + "metadata": { + "collapsed": true + }, + "outputs": [], + "source": [] + }, + { + "cell_type": "markdown", + "metadata": {}, + "source": [ + "#### 13. Create a 10x10 array with random values and find the minimum and maximum values (★☆☆) (suggestion: min, max)" + ] + }, + { + "cell_type": "code", + "execution_count": null, + "metadata": { + "collapsed": false + }, + "outputs": [], + "source": [] + }, + { + "cell_type": "markdown", + "metadata": {}, + "source": [ + "#### 14. Create a random vector of size 30 and find the mean value (★☆☆) (suggestion: mean)" + ] + }, + { + "cell_type": "code", + "execution_count": null, + "metadata": { + "collapsed": false + }, + "outputs": [], + "source": [] + }, + { + "cell_type": "markdown", + "metadata": {}, + "source": [ + "#### 15. Create a 2d array with 1 on the border and 0 inside (★☆☆) (suggestion: array\\[1:-1, 1:-1\\])" + ] + }, + { + "cell_type": "code", + "execution_count": null, + "metadata": { + "collapsed": false + }, + "outputs": [], + "source": [] + }, + { + "cell_type": "markdown", + "metadata": {}, + "source": [ + "#### 16. How to add a border (filled with 0's) around an existing array? (★☆☆) (suggestion: np.pad)" + ] + }, + { + "cell_type": "code", + "execution_count": null, + "metadata": { + "collapsed": false + }, + "outputs": [], + "source": [] + }, + { + "cell_type": "markdown", + "metadata": {}, + "source": [ + "#### 17. What is the result of the following expression? (★☆☆) (suggestion: NaN = not a number, inf = infinity)" + ] + }, + { + "cell_type": "markdown", + "metadata": {}, + "source": [ + "```python\n", + "0 * np.nan\n", + "np.nan == np.nan\n", + "np.inf > np.nan\n", + "np.nan - np.nan\n", + "0.3 == 3 * 0.1\n", + "```" + ] + }, + { + "cell_type": "code", + "execution_count": null, + "metadata": { + "collapsed": false + }, + "outputs": [], + "source": [] + }, + { + "cell_type": "markdown", + "metadata": {}, + "source": [ + "#### 18. Create a 5x5 matrix with values 1,2,3,4 just below the diagonal (★☆☆) (suggestion: np.diag)" + ] + }, + { + "cell_type": "code", + "execution_count": null, + "metadata": { + "collapsed": false + }, + "outputs": [], + "source": [] + }, + { + "cell_type": "markdown", + "metadata": {}, + "source": [ + "#### 19. Create a 8x8 matrix and fill it with a checkerboard pattern (★☆☆) (suggestion: array\\[::2\\])" + ] + }, + { + "cell_type": "code", + "execution_count": null, + "metadata": { + "collapsed": false + }, + "outputs": [], + "source": [] + }, + { + "cell_type": "markdown", + "metadata": {}, + "source": [ + "#### 20. Consider a (6,7,8) shape array, what is the index (x,y,z) of the 100th element? (suggestion: np.unravel_index)" + ] + }, + { + "cell_type": "code", + "execution_count": null, + "metadata": { + "collapsed": false + }, + "outputs": [], + "source": [] + }, + { + "cell_type": "markdown", + "metadata": {}, + "source": [ + "#### 21. Create a checkerboard 8x8 matrix using the tile function (★☆☆) (suggestion: np.tile)" + ] + }, + { + "cell_type": "code", + "execution_count": null, + "metadata": { + "collapsed": false + }, + "outputs": [], + "source": [] + }, + { + "cell_type": "markdown", + "metadata": {}, + "source": [ + "#### 22. Normalize a 5x5 random matrix (★☆☆) (suggestion: (x - min) / (max - min))" + ] + }, + { + "cell_type": "code", + "execution_count": null, + "metadata": { + "collapsed": false + }, + "outputs": [], + "source": [] + }, + { + "cell_type": "markdown", + "metadata": {}, + "source": [ + "#### 23. Create a custom dtype that describes a color as four unsigned bytes (RGBA) (★☆☆) (suggestion: np.dtype)" + ] + }, + { + "cell_type": "code", + "execution_count": null, + "metadata": { + "collapsed": true + }, + "outputs": [], + "source": [] + }, + { + "cell_type": "markdown", + "metadata": {}, + "source": [ + "#### 24. Multiply a 5x3 matrix by a 3x2 matrix (real matrix product) (★☆☆) (suggestion: np.dot | @)" + ] + }, + { + "cell_type": "code", + "execution_count": null, + "metadata": { + "collapsed": false + }, + "outputs": [], + "source": [] + }, + { + "cell_type": "markdown", + "metadata": {}, + "source": [ + "#### 25. Given a 1D array, negate all elements which are between 3 and 8, in place. (★☆☆) (suggestion: >, <=)" + ] + }, + { + "cell_type": "code", + "execution_count": null, + "metadata": { + "collapsed": false + }, + "outputs": [], + "source": [] + }, + { + "cell_type": "markdown", + "metadata": {}, + "source": [ + "#### 26. What is the output of the following script? (★☆☆) (suggestion: np.sum)" + ] + }, + { + "cell_type": "markdown", + "metadata": {}, + "source": [ + "```python\n", + "# Author: Jake VanderPlas\n", + "\n", + "print(sum(range(5),-1))\n", + "from numpy import *\n", + "print(sum(range(5),-1))\n", + "```" + ] + }, + { + "cell_type": "code", + "execution_count": null, + "metadata": { + "collapsed": false + }, + "outputs": [], + "source": [] + }, + { + "cell_type": "markdown", + "metadata": {}, + "source": [ + "#### 27. Consider an integer vector Z, which of these expressions are legal? (★☆☆)" + ] + }, + { + "cell_type": "markdown", + "metadata": {}, + "source": [ + "```python\n", + "Z**Z\n", + "2 << Z >> 2\n", + "Z <- Z\n", + "1j*Z\n", + "Z/1/1\n", + "ZZ\n", + "```" + ] + }, + { + "cell_type": "code", + "execution_count": null, + "metadata": { + "collapsed": false + }, + "outputs": [], + "source": [] + }, + { + "cell_type": "markdown", + "metadata": {}, + "source": [ + "#### 28. What are the result of the following expressions?" + ] + }, + { + "cell_type": "markdown", + "metadata": {}, + "source": [ + "```python\n", + "np.array(0) / np.array(0)\n", + "np.array(0) // np.array(0)\n", + "np.array([np.nan]).astype(int).astype(float)\n", + "```" + ] + }, + { + "cell_type": "code", + "execution_count": null, + "metadata": { + "collapsed": false + }, + "outputs": [], + "source": [] + }, + { + "cell_type": "markdown", + "metadata": {}, + "source": [ + "#### 29. How to round away from zero a float array ? (★☆☆) (suggestion: np.uniform, np.copysign, np.ceil, np.abs)" + ] + }, + { + "cell_type": "code", + "execution_count": null, + "metadata": { + "collapsed": false + }, + "outputs": [], + "source": [] + }, + { + "cell_type": "markdown", + "metadata": {}, + "source": [ + "#### 30. How to find common values between two arrays? (★☆☆) (suggestion: np.intersect1d)" + ] + }, + { + "cell_type": "code", + "execution_count": null, + "metadata": { + "collapsed": false + }, + "outputs": [], + "source": [] + }, + { + "cell_type": "markdown", + "metadata": {}, + "source": [ + "#### 31. How to ignore all numpy warnings (not recommended)? (★☆☆) (suggestion: np.seterr, np.errstate)" + ] + }, + { + "cell_type": "code", + "execution_count": null, + "metadata": { + "collapsed": false + }, + "outputs": [], + "source": [] + }, + { + "cell_type": "markdown", + "metadata": {}, + "source": [ + "#### 32. Is the following expressions true? (★☆☆) (suggestion: imaginary number)" + ] + }, + { + "cell_type": "markdown", + "metadata": {}, + "source": [ + "```python\n", + "np.sqrt(-1) == np.emath.sqrt(-1)\n", + "```" + ] + }, + { + "cell_type": "code", + "execution_count": null, + "metadata": { + "collapsed": false + }, + "outputs": [], + "source": [] + }, + { + "cell_type": "markdown", + "metadata": {}, + "source": [ + "#### 33. How to get the dates of yesterday, today and tomorrow? (★☆☆) (suggestion: np.datetime64, np.timedelta64)" + ] + }, + { + "cell_type": "code", + "execution_count": null, + "metadata": { + "collapsed": true + }, + "outputs": [], + "source": [] + }, + { + "cell_type": "markdown", + "metadata": {}, + "source": [ + "#### 34. How to get all the dates corresponding to the month of July 2016? (★★☆) (suggestion: np.arange(dtype=datetime64\\['D'\\]))" + ] + }, + { + "cell_type": "code", + "execution_count": null, + "metadata": { + "collapsed": false + }, + "outputs": [], + "source": [] + }, + { + "cell_type": "markdown", + "metadata": {}, + "source": [ + "#### 35. How to compute ((A+B)\\*(-A/2)) in place (without copy)? (★★☆) (suggestion: np.add(out=), np.negative(out=), np.multiply(out=), np.divide(out=))" + ] + }, + { + "cell_type": "code", + "execution_count": null, + "metadata": { + "collapsed": false + }, + "outputs": [], + "source": [] + }, + { + "cell_type": "markdown", + "metadata": {}, + "source": [ + "#### 36. Extract the integer part of a random array using 5 different methods (★★☆) (suggestion: %, np.floor, np.ceil, astype, np.trunc)" + ] + }, + { + "cell_type": "code", + "execution_count": null, + "metadata": { + "collapsed": false + }, + "outputs": [], + "source": [] + }, + { + "cell_type": "markdown", + "metadata": {}, + "source": [ + "#### 37. Create a 5x5 matrix with row values ranging from 0 to 4 (★★☆) (suggestion: np.arange)" + ] + }, + { + "cell_type": "code", + "execution_count": null, + "metadata": { + "collapsed": false + }, + "outputs": [], + "source": [] + }, + { + "cell_type": "markdown", + "metadata": {}, + "source": [ + "#### 38. Consider a generator function that generates 10 integers and use it to build an array (★☆☆) (suggestion: np.fromiter)" + ] + }, + { + "cell_type": "code", + "execution_count": null, + "metadata": { + "collapsed": false + }, + "outputs": [], + "source": [] + }, + { + "cell_type": "markdown", + "metadata": {}, + "source": [ + "#### 39. Create a vector of size 10 with values ranging from 0 to 1, both excluded (★★☆) (suggestion: np.linespace)" + ] + }, + { + "cell_type": "code", + "execution_count": null, + "metadata": { + "collapsed": false + }, + "outputs": [], + "source": [] + }, + { + "cell_type": "markdown", + "metadata": {}, + "source": [ + "#### 40. Create a random vector of size 10 and sort it (★★☆) (suggestion: sort)" + ] + }, + { + "cell_type": "code", + "execution_count": null, + "metadata": { + "collapsed": false + }, + "outputs": [], + "source": [] + }, + { + "cell_type": "markdown", + "metadata": {}, + "source": [ + "#### 41. How to sum a small array faster than np.sum? (★★☆) (suggestion: np.add.reduce)" + ] + }, + { + "cell_type": "code", + "execution_count": null, + "metadata": { + "collapsed": false + }, + "outputs": [], + "source": [] + }, + { + "cell_type": "markdown", + "metadata": {}, + "source": [ + "#### 42. Consider two random array A and B, check if they are equal (★★☆) (suggestion: np.allclose, np.array\\_equal)" + ] + }, + { + "cell_type": "code", + "execution_count": null, + "metadata": { + "collapsed": false + }, + "outputs": [], + "source": [] + }, + { + "cell_type": "markdown", + "metadata": {}, + "source": [ + "#### 43. Make an array immutable (read-only) (★★☆) (suggestion: flags.writeable)" + ] + }, + { + "cell_type": "code", + "execution_count": null, + "metadata": { + "collapsed": false + }, + "outputs": [], + "source": [] + }, + { + "cell_type": "markdown", + "metadata": {}, + "source": [ + "#### 44. Consider a random 10x2 matrix representing cartesian coordinates, convert them to polar coordinates (★★☆) (suggestion: np.sqrt, np.arctan2)" + ] + }, + { + "cell_type": "code", + "execution_count": null, + "metadata": { + "collapsed": false + }, + "outputs": [], + "source": [] + }, + { + "cell_type": "markdown", + "metadata": {}, + "source": [ + "#### 45. Create random vector of size 10 and replace the maximum value by 0 (★★☆) (suggestion: argmax)" + ] + }, + { + "cell_type": "code", + "execution_count": null, + "metadata": { + "collapsed": false + }, + "outputs": [], + "source": [] + }, + { + "cell_type": "markdown", + "metadata": {}, + "source": [ + "#### 46. Create a structured array with `x` and `y` coordinates covering the \\[0,1\\]x\\[0,1\\] area (★★☆) (suggestion: np.meshgrid)" + ] + }, + { + "cell_type": "code", + "execution_count": null, + "metadata": { + "collapsed": false + }, + "outputs": [], + "source": [] + }, + { + "cell_type": "markdown", + "metadata": {}, + "source": [ + "#### 47. Given two arrays, X and Y, construct the Cauchy matrix C (Cij =1/(xi - yj)) (suggestion: np.subtract.outer)" + ] + }, + { + "cell_type": "code", + "execution_count": null, + "metadata": { + "collapsed": false + }, + "outputs": [], + "source": [] + }, + { + "cell_type": "markdown", + "metadata": {}, + "source": [ + "#### 48. Print the minimum and maximum representable value for each numpy scalar type (★★☆) (suggestion: np.iinfo, np.finfo, eps)" + ] + }, + { + "cell_type": "code", + "execution_count": null, + "metadata": { + "collapsed": false + }, + "outputs": [], + "source": [] + }, + { + "cell_type": "markdown", + "metadata": {}, + "source": [ + "#### 49. How to print all the values of an array? (★★☆) (suggestion: np.set\\_printoptions)" + ] + }, + { + "cell_type": "code", + "execution_count": null, + "metadata": { + "collapsed": false + }, + "outputs": [], + "source": [] + }, + { + "cell_type": "markdown", + "metadata": {}, + "source": [ + "#### 50. How to find the closest value (to a given scalar) in a vector? (★★☆) (suggestion: argmin)" + ] + }, + { + "cell_type": "code", + "execution_count": null, + "metadata": { + "collapsed": false + }, + "outputs": [], + "source": [] + }, + { + "cell_type": "markdown", + "metadata": {}, + "source": [ + "#### 51. Create a structured array representing a position (x,y) and a color (r,g,b) (★★☆) (suggestion: dtype)" + ] + }, + { + "cell_type": "code", + "execution_count": null, + "metadata": { + "collapsed": false + }, + "outputs": [], + "source": [] + }, + { + "cell_type": "markdown", + "metadata": {}, + "source": [ + "#### 52. Consider a random vector with shape (100,2) representing coordinates, find point by point distances (★★☆) (suggestion: np.atleast\\_2d, T, np.sqrt)" + ] + }, + { + "cell_type": "code", + "execution_count": null, + "metadata": { + "collapsed": false + }, + "outputs": [], + "source": [] + }, + { + "cell_type": "markdown", + "metadata": {}, + "source": [ + "#### 53. How to convert a float (32 bits) array into an integer (32 bits) in place? (suggestion: astype(copy=False))" + ] + }, + { + "cell_type": "code", + "execution_count": null, + "metadata": { + "collapsed": false + }, + "outputs": [], + "source": [] + }, + { + "cell_type": "markdown", + "metadata": {}, + "source": [ + "#### 54. How to read the following file? (★★☆) (suggestion: np.genfromtxt)" + ] + }, + { + "cell_type": "markdown", + "metadata": {}, + "source": [ + "```\n", + "1, 2, 3, 4, 5\n", + "6, , , 7, 8\n", + " , , 9,10,11\n", + "```" + ] + }, + { + "cell_type": "code", + "execution_count": null, + "metadata": { + "collapsed": false + }, + "outputs": [], + "source": [] + }, + { + "cell_type": "markdown", + "metadata": {}, + "source": [ + "#### 55. What is the equivalent of enumerate for numpy arrays? (★★☆) (suggestion: np.ndenumerate, np.ndindex)" + ] + }, + { + "cell_type": "code", + "execution_count": null, + "metadata": { + "collapsed": false + }, + "outputs": [], + "source": [] + }, + { + "cell_type": "markdown", + "metadata": {}, + "source": [ + "#### 56. Generate a generic 2D Gaussian-like array (★★☆) (suggestion: np.meshgrid, np.exp)" + ] + }, + { + "cell_type": "code", + "execution_count": null, + "metadata": { + "collapsed": false + }, + "outputs": [], + "source": [] + }, + { + "cell_type": "markdown", + "metadata": {}, + "source": [ + "#### 57. How to randomly place p elements in a 2D array? (★★☆) (suggestion: np.put, np.random.choice)" + ] + }, + { + "cell_type": "code", + "execution_count": null, + "metadata": { + "collapsed": false + }, + "outputs": [], + "source": [] + }, + { + "cell_type": "markdown", + "metadata": {}, + "source": [ + "#### 58. Subtract the mean of each row of a matrix (★★☆) (suggestion: mean(axis=,keepdims=))" + ] + }, + { + "cell_type": "code", + "execution_count": null, + "metadata": { + "collapsed": false + }, + "outputs": [], + "source": [] + }, + { + "cell_type": "markdown", + "metadata": {}, + "source": [ + "#### 59. How to sort an array by the nth column? (★★☆) (suggestion: argsort)" + ] + }, + { + "cell_type": "code", + "execution_count": null, + "metadata": { + "collapsed": false + }, + "outputs": [], + "source": [] + }, + { + "cell_type": "markdown", + "metadata": {}, + "source": [ + "#### 60. How to tell if a given 2D array has null columns? (★★☆) (suggestion: any, ~)" + ] + }, + { + "cell_type": "code", + "execution_count": null, + "metadata": { + "collapsed": false + }, + "outputs": [], + "source": [] + }, + { + "cell_type": "markdown", + "metadata": {}, + "source": [ + "#### 61. Find the nearest value from a given value in an array (★★☆) (suggestion: np.abs, argmin, flat)" + ] + }, + { + "cell_type": "code", + "execution_count": null, + "metadata": { + "collapsed": false + }, + "outputs": [], + "source": [] + }, + { + "cell_type": "markdown", + "metadata": {}, + "source": [ + "#### 62. Considering two arrays with shape (1,3) and (3,1), how to compute their sum using an iterator? (★★☆) (suggestion: np.nditer)" + ] + }, + { + "cell_type": "code", + "execution_count": null, + "metadata": { + "collapsed": false + }, + "outputs": [], + "source": [] + }, + { + "cell_type": "markdown", + "metadata": {}, + "source": [ + "#### 63. Create an array class that has a name attribute (★★☆) (suggestion: class method)" + ] + }, + { + "cell_type": "code", + "execution_count": null, + "metadata": { + "collapsed": false + }, + "outputs": [], + "source": [] + }, + { + "cell_type": "markdown", + "metadata": {}, + "source": [ + "#### 64. Consider a given vector, how to add 1 to each element indexed by a second vector (be careful with repeated indices)? (★★★) (suggestion: np.bincount | np.add.at)" + ] + }, + { + "cell_type": "code", + "execution_count": null, + "metadata": { + "collapsed": false + }, + "outputs": [], + "source": [] + }, + { + "cell_type": "markdown", + "metadata": {}, + "source": [ + "#### 65. How to accumulate elements of a vector (X) to an array (F) based on an index list (I)? (★★★) (suggestion: np.bincount)" + ] + }, + { + "cell_type": "code", + "execution_count": null, + "metadata": { + "collapsed": false + }, + "outputs": [], + "source": [] + }, + { + "cell_type": "markdown", + "metadata": {}, + "source": [ + "#### 66. Considering a (w,h,3) image of (dtype=ubyte), compute the number of unique colors (★★★) (suggestion: np.unique)" + ] + }, + { + "cell_type": "code", + "execution_count": null, + "metadata": { + "collapsed": false + }, + "outputs": [], + "source": [] + }, + { + "cell_type": "markdown", + "metadata": {}, + "source": [ + "#### 67. Considering a four dimensions array, how to get sum over the last two axis at once? (★★★) (suggestion: sum(axis=(-2,-1)))" + ] + }, + { + "cell_type": "code", + "execution_count": null, + "metadata": { + "collapsed": false + }, + "outputs": [], + "source": [] + }, + { + "cell_type": "markdown", + "metadata": {}, + "source": [ + "#### 68. Considering a one-dimensional vector D, how to compute means of subsets of D using a vector S of same size describing subset indices? (★★★) (suggestion: np.bincount)" + ] + }, + { + "cell_type": "code", + "execution_count": null, + "metadata": { + "collapsed": false + }, + "outputs": [], + "source": [] + }, + { + "cell_type": "markdown", + "metadata": {}, + "source": [ + "#### 69. How to get the diagonal of a dot product? (★★★) (suggestion: np.diag)" + ] + }, + { + "cell_type": "code", + "execution_count": null, + "metadata": { + "collapsed": false + }, + "outputs": [], + "source": [] + }, + { + "cell_type": "markdown", + "metadata": {}, + "source": [ + "#### 70. Consider the vector \\[1, 2, 3, 4, 5\\], how to build a new vector with 3 consecutive zeros interleaved between each value? (★★★) (suggestion: array\\[::4\\])" + ] + }, + { + "cell_type": "code", + "execution_count": null, + "metadata": { + "collapsed": false + }, + "outputs": [], + "source": [] + }, + { + "cell_type": "markdown", + "metadata": {}, + "source": [ + "#### 71. Consider an array of dimension (5,5,3), how to mulitply it by an array with dimensions (5,5)? (★★★) (suggestion: array\\[:, :, None\\])" + ] + }, + { + "cell_type": "code", + "execution_count": null, + "metadata": { + "collapsed": true + }, + "outputs": [], + "source": [] + }, + { + "cell_type": "markdown", + "metadata": {}, + "source": [ + "#### 72. How to swap two rows of an array? (★★★) (suggestion: array\\[\\[\\]\\] = array\\[\\[\\]\\])" + ] + }, + { + "cell_type": "code", + "execution_count": null, + "metadata": { + "collapsed": false + }, + "outputs": [], + "source": [] + }, + { + "cell_type": "markdown", + "metadata": {}, + "source": [ + "#### 73. Consider a set of 10 triplets describing 10 triangles (with shared vertices), find the set of unique line segments composing all the triangles (★★★) (suggestion: repeat, np.roll, np.sort, view, np.unique)" + ] + }, + { + "cell_type": "code", + "execution_count": null, + "metadata": { + "collapsed": false + }, + "outputs": [], + "source": [] + }, + { + "cell_type": "markdown", + "metadata": {}, + "source": [ + "#### 74. Given an array C that is a bincount, how to produce an array A such that np.bincount(A) == C? (★★★) (suggestion: np.repeat)" + ] + }, + { + "cell_type": "code", + "execution_count": null, + "metadata": { + "collapsed": false + }, + "outputs": [], + "source": [] + }, + { + "cell_type": "markdown", + "metadata": {}, + "source": [ + "#### 75. How to compute averages using a sliding window over an array? (★★★) (suggestion: np.cumsum)" + ] + }, + { + "cell_type": "code", + "execution_count": null, + "metadata": { + "collapsed": false + }, + "outputs": [], + "source": [] + }, + { + "cell_type": "markdown", + "metadata": {}, + "source": [ + "#### 76. Consider a one-dimensional array Z, build a two-dimensional array whose first row is (Z\\[0\\],Z\\[1\\],Z\\[2\\]) and each subsequent row is shifted by 1 (last row should be (Z\\[-3\\],Z\\[-2\\],Z\\[-1\\]) (★★★) (suggestion: from numpy.lib import stride_tricks)" + ] + }, + { + "cell_type": "code", + "execution_count": null, + "metadata": { + "collapsed": false + }, + "outputs": [], + "source": [] + }, + { + "cell_type": "markdown", + "metadata": {}, + "source": [ + "#### 77. How to negate a boolean, or to change the sign of a float inplace? (★★★) (suggestion: np.logical_not, np.negative)" + ] + }, + { + "cell_type": "code", + "execution_count": null, + "metadata": { + "collapsed": false + }, + "outputs": [], + "source": [] + }, + { + "cell_type": "markdown", + "metadata": {}, + "source": [ + "#### 78. Consider 2 sets of points P0,P1 describing lines (2d) and a point p, how to compute distance from p to each line i (P0\\[i\\],P1\\[i\\])? (★★★)" + ] + }, + { + "cell_type": "code", + "execution_count": null, + "metadata": { + "collapsed": false + }, + "outputs": [], + "source": [] + }, + { + "cell_type": "markdown", + "metadata": {}, + "source": [ + "#### 79. Consider 2 sets of points P0,P1 describing lines (2d) and a set of points P, how to compute distance from each point j (P\\[j\\]) to each line i (P0\\[i\\],P1\\[i\\])? (★★★)" + ] + }, + { + "cell_type": "code", + "execution_count": null, + "metadata": { + "collapsed": false + }, + "outputs": [], + "source": [] + }, + { + "cell_type": "markdown", + "metadata": {}, + "source": [ + "#### 80. Consider an arbitrary array, write a function that extract a subpart with a fixed shape and centered on a given element (pad with a `fill` value when necessary) (★★★) (suggestion: minimum, maximum)" + ] + }, + { + "cell_type": "code", + "execution_count": null, + "metadata": { + "collapsed": false + }, + "outputs": [], + "source": [] + }, + { + "cell_type": "markdown", + "metadata": {}, + "source": [ + "#### 81. Consider an array Z = \\[1,2,3,4,5,6,7,8,9,10,11,12,13,14\\], how to generate an array R = \\[\\[1,2,3,4\\], \\[2,3,4,5\\], \\[3,4,5,6\\], ..., \\[11,12,13,14\\]\\]? (★★★) (suggestion: stride\\_tricks.as\\_strided)" + ] + }, + { + "cell_type": "code", + "execution_count": null, + "metadata": { + "collapsed": false + }, + "outputs": [], + "source": [] + }, + { + "cell_type": "markdown", + "metadata": {}, + "source": [ + "#### 82. Compute a matrix rank (★★★) (suggestion: np.linalg.svd) (suggestion: np.linalg.svd)" + ] + }, + { + "cell_type": "code", + "execution_count": null, + "metadata": { + "collapsed": false + }, + "outputs": [], + "source": [] + }, + { + "cell_type": "markdown", + "metadata": {}, + "source": [ + "#### 83. How to find the most frequent value in an array? (suggestion: np.bincount, argmax)" + ] + }, + { + "cell_type": "code", + "execution_count": null, + "metadata": { + "collapsed": false + }, + "outputs": [], + "source": [] + }, + { + "cell_type": "markdown", + "metadata": {}, + "source": [ + "#### 84. Extract all the contiguous 3x3 blocks from a random 10x10 matrix (★★★) (suggestion: stride\\_tricks.as\\_strided)" + ] + }, + { + "cell_type": "code", + "execution_count": null, + "metadata": { + "collapsed": false + }, + "outputs": [], + "source": [] + }, + { + "cell_type": "markdown", + "metadata": {}, + "source": [ + "#### 85. Create a 2D array subclass such that Z\\[i,j\\] == Z\\[j,i\\] (★★★) (suggestion: class method)" + ] + }, + { + "cell_type": "code", + "execution_count": null, + "metadata": { + "collapsed": false + }, + "outputs": [], + "source": [] + }, + { + "cell_type": "markdown", + "metadata": {}, + "source": [ + "#### 86. Consider a set of p matrices wich shape (n,n) and a set of p vectors with shape (n,1). How to compute the sum of of the p matrix products at once? (result has shape (n,1)) (★★★) (suggestion: np.tensordot)" + ] + }, + { + "cell_type": "code", + "execution_count": null, + "metadata": { + "collapsed": false + }, + "outputs": [], + "source": [] + }, + { + "cell_type": "markdown", + "metadata": {}, + "source": [ + "#### 87. Consider a 16x16 array, how to get the block-sum (block size is 4x4)? (★★★) (suggestion: np.add.reduceat)" + ] + }, + { + "cell_type": "code", + "execution_count": null, + "metadata": { + "collapsed": false + }, + "outputs": [], + "source": [] + }, + { + "cell_type": "markdown", + "metadata": {}, + "source": [ + "#### 88. How to implement the Game of Life using numpy arrays? (★★★)" + ] + }, + { + "cell_type": "code", + "execution_count": null, + "metadata": { + "collapsed": false + }, + "outputs": [], + "source": [] + }, + { + "cell_type": "markdown", + "metadata": {}, + "source": [ + "#### 89. How to get the n largest values of an array (★★★) (suggestion: np.argsort | np.argpartition)" + ] + }, + { + "cell_type": "code", + "execution_count": null, + "metadata": { + "collapsed": false + }, + "outputs": [], + "source": [] + }, + { + "cell_type": "markdown", + "metadata": {}, + "source": [ + "#### 90. Given an arbitrary number of vectors, build the cartesian product (every combinations of every item) (★★★) (suggestion: np.indices)" + ] + }, + { + "cell_type": "code", + "execution_count": null, + "metadata": { + "collapsed": false, + "scrolled": true + }, + "outputs": [], + "source": [] + }, + { + "cell_type": "markdown", + "metadata": {}, + "source": [ + "#### 91. How to create a record array from a regular array? (★★★) (suggestion: np.core.records.fromarrays)" + ] + }, + { + "cell_type": "code", + "execution_count": null, + "metadata": { + "collapsed": false + }, + "outputs": [], + "source": [] + }, + { + "cell_type": "markdown", + "metadata": {}, + "source": [ + "#### 92. Consider a large vector Z, compute Z to the power of 3 using 3 different methods (★★★) (suggestion: np.power, \\*, np.einsum)" + ] + }, + { + "cell_type": "code", + "execution_count": null, + "metadata": { + "collapsed": false + }, + "outputs": [], + "source": [] + }, + { + "cell_type": "markdown", + "metadata": {}, + "source": [ + "#### 93. Consider two arrays A and B of shape (8,3) and (2,2). How to find rows of A that contain elements of each row of B regardless of the order of the elements in B? (★★★) (suggestion: np.where)" + ] + }, + { + "cell_type": "code", + "execution_count": null, + "metadata": { + "collapsed": false + }, + "outputs": [], + "source": [] + }, + { + "cell_type": "markdown", + "metadata": {}, + "source": [ + "#### 94. Considering a 10x3 matrix, extract rows with unequal values (e.g. \\[2,2,3\\]) (★★★)" + ] + }, + { + "cell_type": "code", + "execution_count": null, + "metadata": { + "collapsed": false + }, + "outputs": [], + "source": [] + }, + { + "cell_type": "markdown", + "metadata": {}, + "source": [ + "#### 95. Convert a vector of ints into a matrix binary representation (★★★) (suggestion: np.unpackbits)" + ] + }, + { + "cell_type": "code", + "execution_count": null, + "metadata": { + "collapsed": false + }, + "outputs": [], + "source": [] + }, + { + "cell_type": "markdown", + "metadata": {}, + "source": [ + "#### 96. Given a two dimensional array, how to extract unique rows? (★★★) (suggestion: np.ascontiguousarray)" + ] + }, + { + "cell_type": "code", + "execution_count": null, + "metadata": { + "collapsed": false + }, + "outputs": [], + "source": [] + }, + { + "cell_type": "markdown", + "metadata": {}, + "source": [ + "#### 97. Considering 2 vectors A & B, write the einsum equivalent of inner, outer, sum, and mul function (★★★) (suggestion: np.einsum)" + ] + }, + { + "cell_type": "code", + "execution_count": null, + "metadata": { + "collapsed": false + }, + "outputs": [], + "source": [] + }, + { + "cell_type": "markdown", + "metadata": {}, + "source": [ + "#### 98. Considering a path described by two vectors (X,Y), how to sample it using equidistant samples (★★★)? (suggestion: np.cumsum, np.interp)" + ] + }, + { + "cell_type": "code", + "execution_count": null, + "metadata": { + "collapsed": true + }, + "outputs": [], + "source": [] + }, + { + "cell_type": "markdown", + "metadata": {}, + "source": [ + "#### 99. Given an integer n and a 2D array X, select from X the rows which can be interpreted as draws from a multinomial distribution with n degrees, i.e., the rows which only contain integers and which sum to n. (★★★) (suggestion: np.logical\\_and.reduce, np.mod)" + ] + }, + { + "cell_type": "code", + "execution_count": null, + "metadata": { + "collapsed": false + }, + "outputs": [], + "source": [] + }, + { + "cell_type": "markdown", + "metadata": {}, + "source": [ + "#### 100. Compute bootstrapped 95% confidence intervals for the mean of a 1D array X (i.e., resample the elements of an array with replacement N times, compute the mean of each sample, and then compute percentiles over the means). (★★★) (suggestion: np.percentile)" + ] + }, + { + "cell_type": "code", + "execution_count": null, + "metadata": { + "collapsed": false + }, + "outputs": [], + "source": [] + } + ], + "metadata": { + "kernelspec": { + "display_name": "Python 3", + "language": "python", + "name": "python3" + }, + "language_info": { + "codemirror_mode": { + "name": "ipython", + "version": 3 + }, + "file_extension": ".py", + "mimetype": "text/x-python", + "name": "python", + "nbconvert_exporter": "python", + "pygments_lexer": "ipython3", + "version": "3.6.0" + } + }, + "nbformat": 4, + "nbformat_minor": 0 +} diff --git a/100 Numpy exercises with suggestion.md b/100 Numpy exercises with suggestion.md new file mode 100644 index 0000000..b2a969b --- /dev/null +++ b/100 Numpy exercises with suggestion.md @@ -0,0 +1,445 @@ + +# 100 numpy exercises with suggestion + +This is a collection of exercises that have been collected in the numpy mailing +list, on stack overflow and in the numpy documentation. I've also created some +to reach the 100 limit. The goal of this collection is to offer a quick +reference for both old and new users but also to provide a set of exercices for +those who teach. + +If you find an error or think you've a better way to solve some of them, feel +free to open an issue at + +#### 1. Import the numpy package under the name `np` (★☆☆) (suggestion: import … as ..) + + + +#### 2. Print the numpy version and the configuration (★☆☆) (suggestion: np.\_\_verison\_\_, np.show\_config) + + + +#### 3. Create a null vector of size 10 (★☆☆) (suggestion: np.zeros) + + + +#### 4. How to find the memory size of any array (★☆☆) (suggestion: size, itemsize) + + + +#### 5. How to get the documentation of the numpy add function from the command line? (★☆☆) (suggestion: np.info) + + + +#### 6. Create a null vector of size 10 but the fifth value which is 1 (★☆☆) (suggestion: array\[4\]) + + + +#### 7. Create a vector with values ranging from 10 to 49 (★☆☆) (suggestion: np.arange) + + + +#### 8. Reverse a vector (first element becomes last) (★☆☆) (suggestion: array\[::-1\]) + + + +#### 9. Create a 3x3 matrix with values ranging from 0 to 8 (★☆☆) (suggestion: reshape) + + + +#### 10. Find indices of non-zero elements from \[1,2,0,0,4,0\] (★☆☆) (suggestion: np.nonzero) + + + +#### 11. Create a 3x3 identity matrix (★☆☆) (suggestion: np.eye) + + + +#### 12. Create a 3x3x3 array with random values (★☆☆) (suggestion: np.random.random) + + + +#### 13. Create a 10x10 array with random values and find the minimum and maximum values (★☆☆) (suggestion: min, max) + + + +#### 14. Create a random vector of size 30 and find the mean value (★☆☆) (suggestion: mean) + + + +#### 15. Create a 2d array with 1 on the border and 0 inside (★☆☆) (suggestion: array\[1:-1, 1:-1\]) + + + +#### 16. How to add a border (filled with 0's) around an existing array? (★☆☆) (suggestion: np.pad) + + + +#### 17. What is the result of the following expression? (★☆☆) (suggestion: NaN = not a number, inf = infinity) + + +```python +0 * np.nan +np.nan == np.nan +np.inf > np.nan +np.nan - np.nan +0.3 == 3 * 0.1 +``` + +#### 18. Create a 5x5 matrix with values 1,2,3,4 just below the diagonal (★☆☆) (suggestion: np.diag) + + + +#### 19. Create a 8x8 matrix and fill it with a checkerboard pattern (★☆☆) (suggestion: array\[::2\]) + + + +#### 20. Consider a (6,7,8) shape array, what is the index (x,y,z) of the 100th element? (suggestion: np.unravel\_index) + + + +#### 21. Create a checkerboard 8x8 matrix using the tile function (★☆☆) (suggestion: np.tile) + + + +#### 22. Normalize a 5x5 random matrix (★☆☆) (suggestion: (x - min) / (max - min)) + + + +#### 23. Create a custom dtype that describes a color as four unsigned bytes (RGBA) (★☆☆) (suggestion: np.dtype) + + + +#### 24. Multiply a 5x3 matrix by a 3x2 matrix (real matrix product) (★☆☆) (suggestion: np.dot | @) + + + +#### 25. Given a 1D array, negate all elements which are between 3 and 8, in place. (★☆☆) (suggestion: >, <=) + + + +#### 26. What is the output of the following script? (★☆☆) (suggestion: np.sum) + + +```python +# Author: Jake VanderPlas + +print(sum(range(5),-1)) +from numpy import * +print(sum(range(5),-1)) +``` + +#### 27. Consider an integer vector Z, which of these expressions are legal? (★☆☆) + + +```python +Z**Z +2 << Z >> 2 +Z <- Z +1j*Z +Z/1/1 +ZZ +``` + +#### 28. What are the result of the following expressions? + + +```python +np.array(0) / np.array(0) +np.array(0) // np.array(0) +np.array([np.nan]).astype(int).astype(float) +``` + +#### 29. How to round away from zero a float array ? (★☆☆) (suggestion: np.uniform, np.copysign, np.ceil, np.abs) + + + +#### 30. How to find common values between two arrays? (★☆☆) (suggestion: np.intersect1d) + + + +#### 31. How to ignore all numpy warnings (not recommended)? (★☆☆) (suggestion: np.seterr, np.errstate) + + + +#### 32. Is the following expressions true? (★☆☆) (suggestion: imaginary number) + + +```python +np.sqrt(-1) == np.emath.sqrt(-1) +``` + +#### 33. How to get the dates of yesterday, today and tomorrow? (★☆☆) (suggestion: np.datetime64, np.timedelta64) + + + +#### 34. How to get all the dates corresponding to the month of July 2016? (★★☆) (suggestion: np.arange(dtype=datetime64\['D'\])) + + + +#### 35. How to compute ((A+B)\*(-A/2)) in place (without copy)? (★★☆) (suggestion: np.add(out=), np.negative(out=), np.multiply(out=), np.divide(out=)) + + + +#### 36. Extract the integer part of a random array using 5 different methods (★★☆) (suggestion: %, np.floor, np.ceil, astype, np.trunc) + + + +#### 37. Create a 5x5 matrix with row values ranging from 0 to 4 (★★☆) (suggestion: np.arange) + + + +#### 38. Consider a generator function that generates 10 integers and use it to build an array (★☆☆) (suggestion: np.fromiter) + + + +#### 39. Create a vector of size 10 with values ranging from 0 to 1, both excluded (★★☆) (suggestion: np.linespace) + + + +#### 40. Create a random vector of size 10 and sort it (★★☆) (suggestion: sort) + + + +#### 41. How to sum a small array faster than np.sum? (★★☆) (suggestion: np.add.reduce) + + + +#### 42. Consider two random array A and B, check if they are equal (★★☆) (suggestion: np.allclose, np.array\_equal) + + + +#### 43. Make an array immutable (read-only) (★★☆) (suggestion: flags.writeable) + + + +#### 44. Consider a random 10x2 matrix representing cartesian coordinates, convert them to polar coordinates (★★☆) (suggestion: np.sqrt, np.arctan2) + + + +#### 45. Create random vector of size 10 and replace the maximum value by 0 (★★☆) (suggestion: argmax) + + + +#### 46. Create a structured array with `x` and `y` coordinates covering the \[0,1\]x\[0,1\] area (★★☆) (suggestion: np.meshgrid) + + + +#### 47. Given two arrays, X and Y, construct the Cauchy matrix C (Cij =1/(xi - yj)) (suggestion: np.subtract.outer) + + + +#### 48. Print the minimum and maximum representable value for each numpy scalar type (★★☆) (suggestion: np.iinfo, np.finfo, eps) + + + +#### 49. How to print all the values of an array? (★★☆) (suggestion: np.set\_printoptions) + + + +#### 50. How to find the closest value (to a given scalar) in a vector? (★★☆) (suggestion: argmin) + + + +#### 51. Create a structured array representing a position (x,y) and a color (r,g,b) (★★☆) (suggestion: dtype) + + + +#### 52. Consider a random vector with shape (100,2) representing coordinates, find point by point distances (★★☆) (suggestion: np.atleast\_2d, T, np.sqrt) + + + +#### 53. How to convert a float (32 bits) array into an integer (32 bits) in place? (suggestion: astype(copy=False)) + + + +#### 54. How to read the following file? (★★☆) (suggestion: np.genfromtxt) + + +``` +1, 2, 3, 4, 5 +6, , , 7, 8 + , , 9,10,11 +``` + +#### 55. What is the equivalent of enumerate for numpy arrays? (★★☆) (suggestion: np.ndenumerate, np.ndindex) + + + +#### 56. Generate a generic 2D Gaussian-like array (★★☆) (suggestion: np.meshgrid, np.exp) + + + +#### 57. How to randomly place p elements in a 2D array? (★★☆) (suggestion: np.put, np.random.choice) + + + +#### 58. Subtract the mean of each row of a matrix (★★☆) (suggestion: mean(axis=,keepdims=)) + + + +#### 59. How to sort an array by the nth column? (★★☆) (suggestion: argsort) + + + +#### 60. How to tell if a given 2D array has null columns? (★★☆) (suggestion: any, ~) + + + +#### 61. Find the nearest value from a given value in an array (★★☆) (suggestion: np.abs, argmin, flat) + + + +#### 62. Considering two arrays with shape (1,3) and (3,1), how to compute their sum using an iterator? (★★☆) (suggestion: np.nditer) + + + +#### 63. Create an array class that has a name attribute (★★☆) (suggestion: class method) + + + +#### 64. Consider a given vector, how to add 1 to each element indexed by a second vector (be careful with repeated indices)? (★★★) (suggestion: np.bincount | np.add.at) + + + +#### 65. How to accumulate elements of a vector (X) to an array (F) based on an index list (I)? (★★★) (suggestion: np.bincount) + + + +#### 66. Considering a (w,h,3) image of (dtype=ubyte), compute the number of unique colors (★★★) (suggestion: np.unique) + + + +#### 67. Considering a four dimensions array, how to get sum over the last two axis at once? (★★★) (suggestion: sum(axis=(-2,-1))) + + + +#### 68. Considering a one-dimensional vector D, how to compute means of subsets of D using a vector S of same size describing subset indices? (★★★) (suggestion: np.bincount) + + + +#### 69. How to get the diagonal of a dot product? (★★★) (suggestion: np.diag) + + + +#### 70. Consider the vector \[1, 2, 3, 4, 5\], how to build a new vector with 3 consecutive zeros interleaved between each value? (★★★) (suggestion: array\[::4\]) + + + +#### 71. Consider an array of dimension (5,5,3), how to mulitply it by an array with dimensions (5,5)? (★★★) (suggestion: array\[:, :, None\]) + + + +#### 72. How to swap two rows of an array? (★★★) (suggestion: array\[\[\]\] = array\[\[\]\]) + + + +#### 73. Consider a set of 10 triplets describing 10 triangles (with shared vertices), find the set of unique line segments composing all the triangles (★★★) (suggestion: repeat, np.roll, np.sort, view, np.unique) + + + +#### 74. Given an array C that is a bincount, how to produce an array A such that np.bincount(A) == C? (★★★) (suggestion: np.repeat) + + + +#### 75. How to compute averages using a sliding window over an array? (★★★) (suggestion: np.cumsum) + + + +#### 76. Consider a one-dimensional array Z, build a two-dimensional array whose first row is (Z\[0\],Z\[1\],Z\[2\]) and each subsequent row is shifted by 1 (last row should be (Z\[-3\],Z\[-2\],Z\[-1\]) (★★★) (suggestion: from numpy.lib import stride\_tricks) + + + +#### 77. How to negate a boolean, or to change the sign of a float inplace? (★★★) (suggestion: np.logical_not, np.negative) + + + +#### 78. Consider 2 sets of points P0,P1 describing lines (2d) and a point p, how to compute distance from p to each line i (P0\[i\],P1\[i\])? (★★★) + + + +#### 79. Consider 2 sets of points P0,P1 describing lines (2d) and a set of points P, how to compute distance from each point j (P\[j\]) to each line i (P0\[i\],P1\[i\])? (★★★) + + + +#### 80. Consider an arbitrary array, write a function that extract a subpart with a fixed shape and centered on a given element (pad with a `fill` value when necessary) (★★★) (suggestion: minimum, maximum) + + + +#### 81. Consider an array Z = \[1,2,3,4,5,6,7,8,9,10,11,12,13,14\], how to generate an array R = \[\[1,2,3,4\], \[2,3,4,5\], \[3,4,5,6\], ..., \[11,12,13,14\]\]? (★★★) (suggestion: stride\_tricks.as\_strided) + + + +#### 82. Compute a matrix rank (★★★) (suggestion: np.linalg.svd) + + + +#### 83. How to find the most frequent value in an array? (suggestion: np.bincount, argmax) + + + +#### 84. Extract all the contiguous 3x3 blocks from a random 10x10 matrix (★★★) (suggestion: stride\_tricks.as\_strided) + + + +#### 85. Create a 2D array subclass such that Z\[i,j\] == Z\[j,i\] (★★★) (suggestion: class method) + + + +#### 86. Consider a set of p matrices wich shape (n,n) and a set of p vectors with shape (n,1). How to compute the sum of of the p matrix products at once? (result has shape (n,1)) (★★★) (suggestion: np.tensordot) + + + +#### 87. Consider a 16x16 array, how to get the block-sum (block size is 4x4)? (★★★) (suggestion: np.add.reduceat) + + + +#### 88. How to implement the Game of Life using numpy arrays? (★★★) + + + +#### 89. How to get the n largest values of an array (★★★) (suggestion: np.argsort | np.argpartition) + + + +#### 90. Given an arbitrary number of vectors, build the cartesian product (every combinations of every item) (★★★) (suggestion: np.indices) + + + +#### 91. How to create a record array from a regular array? (★★★) (suggestion: np.core.records.fromarrays) + + + +#### 92. Consider a large vector Z, compute Z to the power of 3 using 3 different methods (★★★) (suggestion: np.power, \*, np.einsum) + + + +#### 93. Consider two arrays A and B of shape (8,3) and (2,2). How to find rows of A that contain elements of each row of B regardless of the order of the elements in B? (★★★) (suggestion: np.where) + + + +#### 94. Considering a 10x3 matrix, extract rows with unequal values (e.g. \[2,2,3\]) (★★★) + + + +#### 95. Convert a vector of ints into a matrix binary representation (★★★) (suggestion: np.unpackbits) + + + +#### 96. Given a two dimensional array, how to extract unique rows? (★★★) (suggestion: np.ascontiguousarray) + + + +#### 97. Considering 2 vectors A & B, write the einsum equivalent of inner, outer, sum, and mul function (★★★) (suggestion: np.einsum) + + + +#### 98. Considering a path described by two vectors (X,Y), how to sample it using equidistant samples (★★★)? (suggestion: np.cumsum, np.interp) + + + +#### 99. Given an integer n and a 2D array X, select from X the rows which can be interpreted as draws from a multinomial distribution with n degrees, i.e., the rows which only contain integers and which sum to n. (★★★) (suggestion: np.logical\_and.reduce, np.mod) + + + +#### 100. Compute bootstrapped 95% confidence intervals for the mean of a 1D array X (i.e., resample the elements of an array with replacement N times, compute the mean of each sample, and then compute percentiles over the means). (★★★) (suggestion: np.percentile) + From 453fa9fa1465c1da705f712261ff9e899ff29fff Mon Sep 17 00:00:00 2001 From: matianjun1 Date: Sun, 18 Jun 2017 22:46:28 +0800 Subject: [PATCH 2/4] add exercise with hint --- ...ynb => 100 Numpy exercises with hint.ipynb | 284 ++++++++----- ...ion.md => 100 Numpy exercises with hint.md | 378 +++++++++++++----- 2 files changed, 472 insertions(+), 190 deletions(-) rename 100 Numpy exercises with suggestion.ipynb => 100 Numpy exercises with hint.ipynb (81%) rename 100 Numpy exercises with suggestion.md => 100 Numpy exercises with hint.md (56%) diff --git a/100 Numpy exercises with suggestion.ipynb b/100 Numpy exercises with hint.ipynb similarity index 81% rename from 100 Numpy exercises with suggestion.ipynb rename to 100 Numpy exercises with hint.ipynb index 7905b84..d9dd849 100644 --- a/100 Numpy exercises with suggestion.ipynb +++ b/100 Numpy exercises with hint.ipynb @@ -4,7 +4,7 @@ "cell_type": "markdown", "metadata": {}, "source": [ - "# 100 numpy exercises with suggestion\n", + "# 100 numpy exercises with hint\n", "\n", "This is a collection of exercises that have been collected in the numpy mailing list, on stack overflow and in the numpy documentation. The goal of this collection is to offer a quick reference for both old and new users but also to provide a set of exercices for those who teach.\n", "\n", @@ -16,7 +16,8 @@ "cell_type": "markdown", "metadata": {}, "source": [ - "#### 1. Import the numpy package under the name `np` (★☆☆) (suggestion: import … as ..)" + "#### 1. Import the numpy package under the name `np` (★☆☆) \n", + "##### (hint: import … as ..)" ] }, { @@ -32,7 +33,8 @@ "cell_type": "markdown", "metadata": {}, "source": [ - "#### 2. Print the numpy version and the configuration (★☆☆) (suggestion: np.\\_\\_verison\\_\\_, np.show\\_config)" + "#### 2. Print the numpy version and the configuration (★☆☆) \n", + "##### (hint: np.\\_\\_verison\\_\\_, np.show\\_config)" ] }, { @@ -48,7 +50,8 @@ "cell_type": "markdown", "metadata": {}, "source": [ - "#### 3. Create a null vector of size 10 (★☆☆) (suggestion: np.zeros)" + "#### 3. Create a null vector of size 10 (★☆☆) \n", + "##### (hint: np.zeros)" ] }, { @@ -64,7 +67,8 @@ "cell_type": "markdown", "metadata": {}, "source": [ - "#### 4. How to find the memory size of any array (★☆☆) (suggestion: size, itemsize)" + "#### 4. How to find the memory size of any array (★☆☆) \n", + "##### (hint: size, itemsize)" ] }, { @@ -80,7 +84,8 @@ "cell_type": "markdown", "metadata": {}, "source": [ - "#### 5. How to get the documentation of the numpy add function from the command line? (★☆☆) (suggestion: np.info)" + "#### 5. How to get the documentation of the numpy add function from the command line? (★☆☆) \n", + "##### (hint: np.info)" ] }, { @@ -96,7 +101,8 @@ "cell_type": "markdown", "metadata": {}, "source": [ - "#### 6. Create a null vector of size 10 but the fifth value which is 1 (★☆☆) (suggestion: array\\[4\\])" + "#### 6. Create a null vector of size 10 but the fifth value which is 1 (★☆☆) \n", + "##### (hint: array\\[4\\])" ] }, { @@ -112,7 +118,8 @@ "cell_type": "markdown", "metadata": {}, "source": [ - "#### 7. Create a vector with values ranging from 10 to 49 (★☆☆) (suggestion: np.arange)" + "#### 7. Create a vector with values ranging from 10 to 49 (★☆☆) \n", + "##### (hint: np.arange)" ] }, { @@ -128,7 +135,8 @@ "cell_type": "markdown", "metadata": {}, "source": [ - "#### 8. Reverse a vector (first element becomes last) (★☆☆) (suggestion: array\\[::-1\\])" + "#### 8. Reverse a vector (first element becomes last) (★☆☆) \n", + "##### (hint: array\\[::-1\\])" ] }, { @@ -144,7 +152,8 @@ "cell_type": "markdown", "metadata": {}, "source": [ - "#### 9. Create a 3x3 matrix with values ranging from 0 to 8 (★☆☆) (suggestion: reshape)" + "#### 9. Create a 3x3 matrix with values ranging from 0 to 8 (★☆☆) \n", + "##### (hint: reshape)" ] }, { @@ -160,7 +169,8 @@ "cell_type": "markdown", "metadata": {}, "source": [ - "#### 10. Find indices of non-zero elements from \\[1,2,0,0,4,0\\] (★☆☆) (suggestion: np.nonzero)" + "#### 10. Find indices of non-zero elements from \\[1,2,0,0,4,0\\] (★☆☆) \n", + "##### (hint: np.nonzero)" ] }, { @@ -176,7 +186,8 @@ "cell_type": "markdown", "metadata": {}, "source": [ - "#### 11. Create a 3x3 identity matrix (★☆☆) (suggestion: np.eye)" + "#### 11. Create a 3x3 identity matrix (★☆☆) \n", + "##### (hint: np.eye)" ] }, { @@ -192,7 +203,8 @@ "cell_type": "markdown", "metadata": {}, "source": [ - "#### 12. Create a 3x3x3 array with random values (★☆☆) (suggestion: np.random.random)" + "#### 12. Create a 3x3x3 array with random values (★☆☆) \n", + "##### (hint: np.random.random)" ] }, { @@ -208,7 +220,8 @@ "cell_type": "markdown", "metadata": {}, "source": [ - "#### 13. Create a 10x10 array with random values and find the minimum and maximum values (★☆☆) (suggestion: min, max)" + "#### 13. Create a 10x10 array with random values and find the minimum and maximum values (★☆☆) \n", + "##### (hint: min, max)" ] }, { @@ -224,7 +237,8 @@ "cell_type": "markdown", "metadata": {}, "source": [ - "#### 14. Create a random vector of size 30 and find the mean value (★☆☆) (suggestion: mean)" + "#### 14. Create a random vector of size 30 and find the mean value (★☆☆) \n", + "##### (hint: mean)" ] }, { @@ -240,7 +254,8 @@ "cell_type": "markdown", "metadata": {}, "source": [ - "#### 15. Create a 2d array with 1 on the border and 0 inside (★☆☆) (suggestion: array\\[1:-1, 1:-1\\])" + "#### 15. Create a 2d array with 1 on the border and 0 inside (★☆☆) \n", + "##### (hint: array\\[1:-1, 1:-1\\])" ] }, { @@ -256,7 +271,8 @@ "cell_type": "markdown", "metadata": {}, "source": [ - "#### 16. How to add a border (filled with 0's) around an existing array? (★☆☆) (suggestion: np.pad)" + "#### 16. How to add a border (filled with 0's) around an existing array? (★☆☆) \n", + "##### (hint: np.pad)" ] }, { @@ -272,7 +288,8 @@ "cell_type": "markdown", "metadata": {}, "source": [ - "#### 17. What is the result of the following expression? (★☆☆) (suggestion: NaN = not a number, inf = infinity)" + "#### 17. What is the result of the following expression? (★☆☆) \n", + "##### (hint: NaN = not a number, inf = infinity)" ] }, { @@ -301,7 +318,8 @@ "cell_type": "markdown", "metadata": {}, "source": [ - "#### 18. Create a 5x5 matrix with values 1,2,3,4 just below the diagonal (★☆☆) (suggestion: np.diag)" + "#### 18. Create a 5x5 matrix with values 1,2,3,4 just below the diagonal (★☆☆) \n", + "##### (hint: np.diag)" ] }, { @@ -317,7 +335,8 @@ "cell_type": "markdown", "metadata": {}, "source": [ - "#### 19. Create a 8x8 matrix and fill it with a checkerboard pattern (★☆☆) (suggestion: array\\[::2\\])" + "#### 19. Create a 8x8 matrix and fill it with a checkerboard pattern (★☆☆) \n", + "##### (hint: array\\[::2\\])" ] }, { @@ -333,7 +352,8 @@ "cell_type": "markdown", "metadata": {}, "source": [ - "#### 20. Consider a (6,7,8) shape array, what is the index (x,y,z) of the 100th element? (suggestion: np.unravel_index)" + "#### 20. Consider a (6,7,8) shape array, what is the index (x,y,z) of the 100th element? \n", + "##### (hint: np.unravel_index)" ] }, { @@ -349,7 +369,8 @@ "cell_type": "markdown", "metadata": {}, "source": [ - "#### 21. Create a checkerboard 8x8 matrix using the tile function (★☆☆) (suggestion: np.tile)" + "#### 21. Create a checkerboard 8x8 matrix using the tile function (★☆☆) \n", + "##### (hint: np.tile)" ] }, { @@ -365,7 +386,8 @@ "cell_type": "markdown", "metadata": {}, "source": [ - "#### 22. Normalize a 5x5 random matrix (★☆☆) (suggestion: (x - min) / (max - min))" + "#### 22. Normalize a 5x5 random matrix (★☆☆) \n", + "##### (hint: (x - min) / (max - min))" ] }, { @@ -381,7 +403,8 @@ "cell_type": "markdown", "metadata": {}, "source": [ - "#### 23. Create a custom dtype that describes a color as four unsigned bytes (RGBA) (★☆☆) (suggestion: np.dtype)" + "#### 23. Create a custom dtype that describes a color as four unsigned bytes (RGBA) (★☆☆) \n", + "##### (hint: np.dtype)" ] }, { @@ -397,7 +420,8 @@ "cell_type": "markdown", "metadata": {}, "source": [ - "#### 24. Multiply a 5x3 matrix by a 3x2 matrix (real matrix product) (★☆☆) (suggestion: np.dot | @)" + "#### 24. Multiply a 5x3 matrix by a 3x2 matrix (real matrix product) (★☆☆) \n", + "##### (hint: np.dot | @)" ] }, { @@ -413,7 +437,8 @@ "cell_type": "markdown", "metadata": {}, "source": [ - "#### 25. Given a 1D array, negate all elements which are between 3 and 8, in place. (★☆☆) (suggestion: >, <=)" + "#### 25. Given a 1D array, negate all elements which are between 3 and 8, in place. (★☆☆) \n", + "##### (hint: >, <=)" ] }, { @@ -429,7 +454,8 @@ "cell_type": "markdown", "metadata": {}, "source": [ - "#### 26. What is the output of the following script? (★☆☆) (suggestion: np.sum)" + "#### 26. What is the output of the following script? (★☆☆) \n", + "##### (hint: np.sum)" ] }, { @@ -515,7 +541,8 @@ "cell_type": "markdown", "metadata": {}, "source": [ - "#### 29. How to round away from zero a float array ? (★☆☆) (suggestion: np.uniform, np.copysign, np.ceil, np.abs)" + "#### 29. How to round away from zero a float array ? (★☆☆) \n", + "##### (hint: np.uniform, np.copysign, np.ceil, np.abs)" ] }, { @@ -531,7 +558,8 @@ "cell_type": "markdown", "metadata": {}, "source": [ - "#### 30. How to find common values between two arrays? (★☆☆) (suggestion: np.intersect1d)" + "#### 30. How to find common values between two arrays? (★☆☆) \n", + "##### (hint: np.intersect1d)" ] }, { @@ -547,7 +575,8 @@ "cell_type": "markdown", "metadata": {}, "source": [ - "#### 31. How to ignore all numpy warnings (not recommended)? (★☆☆) (suggestion: np.seterr, np.errstate)" + "#### 31. How to ignore all numpy warnings (not recommended)? (★☆☆) \n", + "##### (hint: np.seterr, np.errstate)" ] }, { @@ -563,7 +592,8 @@ "cell_type": "markdown", "metadata": {}, "source": [ - "#### 32. Is the following expressions true? (★☆☆) (suggestion: imaginary number)" + "#### 32. Is the following expressions true? (★☆☆) \n", + "##### (hint: imaginary number)" ] }, { @@ -588,7 +618,8 @@ "cell_type": "markdown", "metadata": {}, "source": [ - "#### 33. How to get the dates of yesterday, today and tomorrow? (★☆☆) (suggestion: np.datetime64, np.timedelta64)" + "#### 33. How to get the dates of yesterday, today and tomorrow? (★☆☆) \n", + "##### (hint: np.datetime64, np.timedelta64)" ] }, { @@ -604,7 +635,8 @@ "cell_type": "markdown", "metadata": {}, "source": [ - "#### 34. How to get all the dates corresponding to the month of July 2016? (★★☆) (suggestion: np.arange(dtype=datetime64\\['D'\\]))" + "#### 34. How to get all the dates corresponding to the month of July 2016? (★★☆) \n", + "##### (hint: np.arange(dtype=datetime64\\['D'\\]))" ] }, { @@ -620,7 +652,8 @@ "cell_type": "markdown", "metadata": {}, "source": [ - "#### 35. How to compute ((A+B)\\*(-A/2)) in place (without copy)? (★★☆) (suggestion: np.add(out=), np.negative(out=), np.multiply(out=), np.divide(out=))" + "#### 35. How to compute ((A+B)\\*(-A/2)) in place (without copy)? (★★☆) \n", + "##### (hint: np.add(out=), np.negative(out=), np.multiply(out=), np.divide(out=))" ] }, { @@ -636,7 +669,8 @@ "cell_type": "markdown", "metadata": {}, "source": [ - "#### 36. Extract the integer part of a random array using 5 different methods (★★☆) (suggestion: %, np.floor, np.ceil, astype, np.trunc)" + "#### 36. Extract the integer part of a random array using 5 different methods (★★☆) \n", + "##### (hint: %, np.floor, np.ceil, astype, np.trunc)" ] }, { @@ -652,7 +686,8 @@ "cell_type": "markdown", "metadata": {}, "source": [ - "#### 37. Create a 5x5 matrix with row values ranging from 0 to 4 (★★☆) (suggestion: np.arange)" + "#### 37. Create a 5x5 matrix with row values ranging from 0 to 4 (★★☆) \n", + "##### (hint: np.arange)" ] }, { @@ -668,7 +703,8 @@ "cell_type": "markdown", "metadata": {}, "source": [ - "#### 38. Consider a generator function that generates 10 integers and use it to build an array (★☆☆) (suggestion: np.fromiter)" + "#### 38. Consider a generator function that generates 10 integers and use it to build an array (★☆☆) \n", + "##### (hint: np.fromiter)" ] }, { @@ -684,7 +720,8 @@ "cell_type": "markdown", "metadata": {}, "source": [ - "#### 39. Create a vector of size 10 with values ranging from 0 to 1, both excluded (★★☆) (suggestion: np.linespace)" + "#### 39. Create a vector of size 10 with values ranging from 0 to 1, both excluded (★★☆) \n", + "##### (hint: np.linespace)" ] }, { @@ -700,7 +737,8 @@ "cell_type": "markdown", "metadata": {}, "source": [ - "#### 40. Create a random vector of size 10 and sort it (★★☆) (suggestion: sort)" + "#### 40. Create a random vector of size 10 and sort it (★★☆) \n", + "##### (hint: sort)" ] }, { @@ -716,7 +754,8 @@ "cell_type": "markdown", "metadata": {}, "source": [ - "#### 41. How to sum a small array faster than np.sum? (★★☆) (suggestion: np.add.reduce)" + "#### 41. How to sum a small array faster than np.sum? (★★☆) \n", + "##### (hint: np.add.reduce)" ] }, { @@ -732,7 +771,8 @@ "cell_type": "markdown", "metadata": {}, "source": [ - "#### 42. Consider two random array A and B, check if they are equal (★★☆) (suggestion: np.allclose, np.array\\_equal)" + "#### 42. Consider two random array A and B, check if they are equal (★★☆) \n", + "##### (hint: np.allclose, np.array\\_equal)" ] }, { @@ -748,7 +788,8 @@ "cell_type": "markdown", "metadata": {}, "source": [ - "#### 43. Make an array immutable (read-only) (★★☆) (suggestion: flags.writeable)" + "#### 43. Make an array immutable (read-only) (★★☆) \n", + "##### (hint: flags.writeable)" ] }, { @@ -764,7 +805,8 @@ "cell_type": "markdown", "metadata": {}, "source": [ - "#### 44. Consider a random 10x2 matrix representing cartesian coordinates, convert them to polar coordinates (★★☆) (suggestion: np.sqrt, np.arctan2)" + "#### 44. Consider a random 10x2 matrix representing cartesian coordinates, convert them to polar coordinates (★★☆) \n", + "##### (hint: np.sqrt, np.arctan2)" ] }, { @@ -780,7 +822,8 @@ "cell_type": "markdown", "metadata": {}, "source": [ - "#### 45. Create random vector of size 10 and replace the maximum value by 0 (★★☆) (suggestion: argmax)" + "#### 45. Create random vector of size 10 and replace the maximum value by 0 (★★☆) \n", + "##### (hint: argmax)" ] }, { @@ -796,7 +839,8 @@ "cell_type": "markdown", "metadata": {}, "source": [ - "#### 46. Create a structured array with `x` and `y` coordinates covering the \\[0,1\\]x\\[0,1\\] area (★★☆) (suggestion: np.meshgrid)" + "#### 46. Create a structured array with `x` and `y` coordinates covering the \\[0,1\\]x\\[0,1\\] area (★★☆) \n", + "##### (hint: np.meshgrid)" ] }, { @@ -812,7 +856,8 @@ "cell_type": "markdown", "metadata": {}, "source": [ - "#### 47. Given two arrays, X and Y, construct the Cauchy matrix C (Cij =1/(xi - yj)) (suggestion: np.subtract.outer)" + "#### 47. Given two arrays, X and Y, construct the Cauchy matrix C (Cij =1/(xi - yj)) \n", + "##### (hint: np.subtract.outer)" ] }, { @@ -828,7 +873,8 @@ "cell_type": "markdown", "metadata": {}, "source": [ - "#### 48. Print the minimum and maximum representable value for each numpy scalar type (★★☆) (suggestion: np.iinfo, np.finfo, eps)" + "#### 48. Print the minimum and maximum representable value for each numpy scalar type (★★☆) \n", + "##### (hint: np.iinfo, np.finfo, eps)" ] }, { @@ -844,7 +890,8 @@ "cell_type": "markdown", "metadata": {}, "source": [ - "#### 49. How to print all the values of an array? (★★☆) (suggestion: np.set\\_printoptions)" + "#### 49. How to print all the values of an array? (★★☆) \n", + "##### (hint: np.set\\_printoptions)" ] }, { @@ -860,7 +907,8 @@ "cell_type": "markdown", "metadata": {}, "source": [ - "#### 50. How to find the closest value (to a given scalar) in a vector? (★★☆) (suggestion: argmin)" + "#### 50. How to find the closest value (to a given scalar) in a vector? (★★☆) \n", + "##### (hint: argmin)" ] }, { @@ -876,7 +924,8 @@ "cell_type": "markdown", "metadata": {}, "source": [ - "#### 51. Create a structured array representing a position (x,y) and a color (r,g,b) (★★☆) (suggestion: dtype)" + "#### 51. Create a structured array representing a position (x,y) and a color (r,g,b) (★★☆) \n", + "##### (hint: dtype)" ] }, { @@ -892,7 +941,8 @@ "cell_type": "markdown", "metadata": {}, "source": [ - "#### 52. Consider a random vector with shape (100,2) representing coordinates, find point by point distances (★★☆) (suggestion: np.atleast\\_2d, T, np.sqrt)" + "#### 52. Consider a random vector with shape (100,2) representing coordinates, find point by point distances (★★☆) \n", + "##### (hint: np.atleast\\_2d, T, np.sqrt)" ] }, { @@ -908,7 +958,8 @@ "cell_type": "markdown", "metadata": {}, "source": [ - "#### 53. How to convert a float (32 bits) array into an integer (32 bits) in place? (suggestion: astype(copy=False))" + "#### 53. How to convert a float (32 bits) array into an integer (32 bits) in place? \n", + "##### (hint: astype(copy=False))" ] }, { @@ -924,7 +975,8 @@ "cell_type": "markdown", "metadata": {}, "source": [ - "#### 54. How to read the following file? (★★☆) (suggestion: np.genfromtxt)" + "#### 54. How to read the following file? (★★☆) \n", + "##### (hint: np.genfromtxt)" ] }, { @@ -951,7 +1003,8 @@ "cell_type": "markdown", "metadata": {}, "source": [ - "#### 55. What is the equivalent of enumerate for numpy arrays? (★★☆) (suggestion: np.ndenumerate, np.ndindex)" + "#### 55. What is the equivalent of enumerate for numpy arrays? (★★☆) \n", + "##### (hint: np.ndenumerate, np.ndindex)" ] }, { @@ -967,7 +1020,8 @@ "cell_type": "markdown", "metadata": {}, "source": [ - "#### 56. Generate a generic 2D Gaussian-like array (★★☆) (suggestion: np.meshgrid, np.exp)" + "#### 56. Generate a generic 2D Gaussian-like array (★★☆) \n", + "##### (hint: np.meshgrid, np.exp)" ] }, { @@ -983,7 +1037,8 @@ "cell_type": "markdown", "metadata": {}, "source": [ - "#### 57. How to randomly place p elements in a 2D array? (★★☆) (suggestion: np.put, np.random.choice)" + "#### 57. How to randomly place p elements in a 2D array? (★★☆) \n", + "##### (hint: np.put, np.random.choice)" ] }, { @@ -999,7 +1054,8 @@ "cell_type": "markdown", "metadata": {}, "source": [ - "#### 58. Subtract the mean of each row of a matrix (★★☆) (suggestion: mean(axis=,keepdims=))" + "#### 58. Subtract the mean of each row of a matrix (★★☆) \n", + "##### (hint: mean(axis=,keepdims=))" ] }, { @@ -1015,7 +1071,8 @@ "cell_type": "markdown", "metadata": {}, "source": [ - "#### 59. How to sort an array by the nth column? (★★☆) (suggestion: argsort)" + "#### 59. How to sort an array by the nth column? (★★☆) \n", + "##### (hint: argsort)" ] }, { @@ -1031,7 +1088,8 @@ "cell_type": "markdown", "metadata": {}, "source": [ - "#### 60. How to tell if a given 2D array has null columns? (★★☆) (suggestion: any, ~)" + "#### 60. How to tell if a given 2D array has null columns? (★★☆) \n", + "##### (hint: any, ~)" ] }, { @@ -1047,7 +1105,8 @@ "cell_type": "markdown", "metadata": {}, "source": [ - "#### 61. Find the nearest value from a given value in an array (★★☆) (suggestion: np.abs, argmin, flat)" + "#### 61. Find the nearest value from a given value in an array (★★☆) \n", + "##### (hint: np.abs, argmin, flat)" ] }, { @@ -1063,7 +1122,8 @@ "cell_type": "markdown", "metadata": {}, "source": [ - "#### 62. Considering two arrays with shape (1,3) and (3,1), how to compute their sum using an iterator? (★★☆) (suggestion: np.nditer)" + "#### 62. Considering two arrays with shape (1,3) and (3,1), how to compute their sum using an iterator? (★★☆) \n", + "##### (hint: np.nditer)" ] }, { @@ -1079,7 +1139,8 @@ "cell_type": "markdown", "metadata": {}, "source": [ - "#### 63. Create an array class that has a name attribute (★★☆) (suggestion: class method)" + "#### 63. Create an array class that has a name attribute (★★☆) \n", + "##### (hint: class method)" ] }, { @@ -1095,7 +1156,8 @@ "cell_type": "markdown", "metadata": {}, "source": [ - "#### 64. Consider a given vector, how to add 1 to each element indexed by a second vector (be careful with repeated indices)? (★★★) (suggestion: np.bincount | np.add.at)" + "#### 64. Consider a given vector, how to add 1 to each element indexed by a second vector (be careful with repeated indices)? (★★★) \n", + "##### (hint: np.bincount | np.add.at)" ] }, { @@ -1111,7 +1173,8 @@ "cell_type": "markdown", "metadata": {}, "source": [ - "#### 65. How to accumulate elements of a vector (X) to an array (F) based on an index list (I)? (★★★) (suggestion: np.bincount)" + "#### 65. How to accumulate elements of a vector (X) to an array (F) based on an index list (I)? (★★★) \n", + "##### (hint: np.bincount)" ] }, { @@ -1127,7 +1190,8 @@ "cell_type": "markdown", "metadata": {}, "source": [ - "#### 66. Considering a (w,h,3) image of (dtype=ubyte), compute the number of unique colors (★★★) (suggestion: np.unique)" + "#### 66. Considering a (w,h,3) image of (dtype=ubyte), compute the number of unique colors (★★★) \n", + "##### (hint: np.unique)" ] }, { @@ -1143,7 +1207,8 @@ "cell_type": "markdown", "metadata": {}, "source": [ - "#### 67. Considering a four dimensions array, how to get sum over the last two axis at once? (★★★) (suggestion: sum(axis=(-2,-1)))" + "#### 67. Considering a four dimensions array, how to get sum over the last two axis at once? (★★★) \n", + "##### (hint: sum(axis=(-2,-1)))" ] }, { @@ -1159,7 +1224,8 @@ "cell_type": "markdown", "metadata": {}, "source": [ - "#### 68. Considering a one-dimensional vector D, how to compute means of subsets of D using a vector S of same size describing subset indices? (★★★) (suggestion: np.bincount)" + "#### 68. Considering a one-dimensional vector D, how to compute means of subsets of D using a vector S of same size describing subset indices? (★★★) \n", + "##### (hint: np.bincount)" ] }, { @@ -1175,7 +1241,8 @@ "cell_type": "markdown", "metadata": {}, "source": [ - "#### 69. How to get the diagonal of a dot product? (★★★) (suggestion: np.diag)" + "#### 69. How to get the diagonal of a dot product? (★★★) \n", + "##### (hint: np.diag)" ] }, { @@ -1191,7 +1258,8 @@ "cell_type": "markdown", "metadata": {}, "source": [ - "#### 70. Consider the vector \\[1, 2, 3, 4, 5\\], how to build a new vector with 3 consecutive zeros interleaved between each value? (★★★) (suggestion: array\\[::4\\])" + "#### 70. Consider the vector \\[1, 2, 3, 4, 5\\], how to build a new vector with 3 consecutive zeros interleaved between each value? (★★★) \n", + "##### (hint: array\\[::4\\])" ] }, { @@ -1207,7 +1275,8 @@ "cell_type": "markdown", "metadata": {}, "source": [ - "#### 71. Consider an array of dimension (5,5,3), how to mulitply it by an array with dimensions (5,5)? (★★★) (suggestion: array\\[:, :, None\\])" + "#### 71. Consider an array of dimension (5,5,3), how to mulitply it by an array with dimensions (5,5)? (★★★) \n", + "##### (hint: array\\[:, :, None\\])" ] }, { @@ -1223,7 +1292,8 @@ "cell_type": "markdown", "metadata": {}, "source": [ - "#### 72. How to swap two rows of an array? (★★★) (suggestion: array\\[\\[\\]\\] = array\\[\\[\\]\\])" + "#### 72. How to swap two rows of an array? (★★★) \n", + "##### (hint: array\\[\\[\\]\\] = array\\[\\[\\]\\])" ] }, { @@ -1239,7 +1309,8 @@ "cell_type": "markdown", "metadata": {}, "source": [ - "#### 73. Consider a set of 10 triplets describing 10 triangles (with shared vertices), find the set of unique line segments composing all the triangles (★★★) (suggestion: repeat, np.roll, np.sort, view, np.unique)" + "#### 73. Consider a set of 10 triplets describing 10 triangles (with shared vertices), find the set of unique line segments composing all the triangles (★★★) \n", + "##### (hint: repeat, np.roll, np.sort, view, np.unique)" ] }, { @@ -1255,7 +1326,8 @@ "cell_type": "markdown", "metadata": {}, "source": [ - "#### 74. Given an array C that is a bincount, how to produce an array A such that np.bincount(A) == C? (★★★) (suggestion: np.repeat)" + "#### 74. Given an array C that is a bincount, how to produce an array A such that np.bincount(A) == C? (★★★) \n", + "##### (hint: np.repeat)" ] }, { @@ -1271,7 +1343,8 @@ "cell_type": "markdown", "metadata": {}, "source": [ - "#### 75. How to compute averages using a sliding window over an array? (★★★) (suggestion: np.cumsum)" + "#### 75. How to compute averages using a sliding window over an array? (★★★) \n", + "##### (hint: np.cumsum)" ] }, { @@ -1287,7 +1360,8 @@ "cell_type": "markdown", "metadata": {}, "source": [ - "#### 76. Consider a one-dimensional array Z, build a two-dimensional array whose first row is (Z\\[0\\],Z\\[1\\],Z\\[2\\]) and each subsequent row is shifted by 1 (last row should be (Z\\[-3\\],Z\\[-2\\],Z\\[-1\\]) (★★★) (suggestion: from numpy.lib import stride_tricks)" + "#### 76. Consider a one-dimensional array Z, build a two-dimensional array whose first row is (Z\\[0\\],Z\\[1\\],Z\\[2\\]) and each subsequent row is shifted by 1 (last row should be (Z\\[-3\\],Z\\[-2\\],Z\\[-1\\]) (★★★) \n", + "##### (hint: from numpy.lib import stride_tricks)" ] }, { @@ -1303,7 +1377,8 @@ "cell_type": "markdown", "metadata": {}, "source": [ - "#### 77. How to negate a boolean, or to change the sign of a float inplace? (★★★) (suggestion: np.logical_not, np.negative)" + "#### 77. How to negate a boolean, or to change the sign of a float inplace? (★★★) \n", + "##### (hint: np.logical_not, np.negative)" ] }, { @@ -1351,7 +1426,8 @@ "cell_type": "markdown", "metadata": {}, "source": [ - "#### 80. Consider an arbitrary array, write a function that extract a subpart with a fixed shape and centered on a given element (pad with a `fill` value when necessary) (★★★) (suggestion: minimum, maximum)" + "#### 80. Consider an arbitrary array, write a function that extract a subpart with a fixed shape and centered on a given element (pad with a `fill` value when necessary) (★★★) \n", + "##### (hint: minimum, maximum)" ] }, { @@ -1367,7 +1443,8 @@ "cell_type": "markdown", "metadata": {}, "source": [ - "#### 81. Consider an array Z = \\[1,2,3,4,5,6,7,8,9,10,11,12,13,14\\], how to generate an array R = \\[\\[1,2,3,4\\], \\[2,3,4,5\\], \\[3,4,5,6\\], ..., \\[11,12,13,14\\]\\]? (★★★) (suggestion: stride\\_tricks.as\\_strided)" + "#### 81. Consider an array Z = \\[1,2,3,4,5,6,7,8,9,10,11,12,13,14\\], how to generate an array R = \\[\\[1,2,3,4\\], \\[2,3,4,5\\], \\[3,4,5,6\\], ..., \\[11,12,13,14\\]\\]? (★★★) \n", + "##### (hint: stride\\_tricks.as\\_strided)" ] }, { @@ -1383,7 +1460,8 @@ "cell_type": "markdown", "metadata": {}, "source": [ - "#### 82. Compute a matrix rank (★★★) (suggestion: np.linalg.svd) (suggestion: np.linalg.svd)" + "#### 82. Compute a matrix rank (★★★) \n", + "##### (hint: np.linalg.svd) (suggestion: np.linalg.svd)" ] }, { @@ -1399,7 +1477,8 @@ "cell_type": "markdown", "metadata": {}, "source": [ - "#### 83. How to find the most frequent value in an array? (suggestion: np.bincount, argmax)" + "#### 83. How to find the most frequent value in an array? \n", + "##### (hint: np.bincount, argmax)" ] }, { @@ -1415,7 +1494,8 @@ "cell_type": "markdown", "metadata": {}, "source": [ - "#### 84. Extract all the contiguous 3x3 blocks from a random 10x10 matrix (★★★) (suggestion: stride\\_tricks.as\\_strided)" + "#### 84. Extract all the contiguous 3x3 blocks from a random 10x10 matrix (★★★) \n", + "##### (hint: stride\\_tricks.as\\_strided)" ] }, { @@ -1431,7 +1511,8 @@ "cell_type": "markdown", "metadata": {}, "source": [ - "#### 85. Create a 2D array subclass such that Z\\[i,j\\] == Z\\[j,i\\] (★★★) (suggestion: class method)" + "#### 85. Create a 2D array subclass such that Z\\[i,j\\] == Z\\[j,i\\] (★★★) \n", + "##### (hint: class method)" ] }, { @@ -1447,7 +1528,8 @@ "cell_type": "markdown", "metadata": {}, "source": [ - "#### 86. Consider a set of p matrices wich shape (n,n) and a set of p vectors with shape (n,1). How to compute the sum of of the p matrix products at once? (result has shape (n,1)) (★★★) (suggestion: np.tensordot)" + "#### 86. Consider a set of p matrices wich shape (n,n) and a set of p vectors with shape (n,1). How to compute the sum of of the p matrix products at once? (result has shape (n,1)) (★★★) \n", + "##### (hint: np.tensordot)" ] }, { @@ -1463,7 +1545,8 @@ "cell_type": "markdown", "metadata": {}, "source": [ - "#### 87. Consider a 16x16 array, how to get the block-sum (block size is 4x4)? (★★★) (suggestion: np.add.reduceat)" + "#### 87. Consider a 16x16 array, how to get the block-sum (block size is 4x4)? (★★★) \n", + "##### (hint: np.add.reduceat)" ] }, { @@ -1495,7 +1578,8 @@ "cell_type": "markdown", "metadata": {}, "source": [ - "#### 89. How to get the n largest values of an array (★★★) (suggestion: np.argsort | np.argpartition)" + "#### 89. How to get the n largest values of an array (★★★) \n", + "##### (hint: np.argsort | np.argpartition)" ] }, { @@ -1511,7 +1595,8 @@ "cell_type": "markdown", "metadata": {}, "source": [ - "#### 90. Given an arbitrary number of vectors, build the cartesian product (every combinations of every item) (★★★) (suggestion: np.indices)" + "#### 90. Given an arbitrary number of vectors, build the cartesian product (every combinations of every item) (★★★) \n", + "##### (hint: np.indices)" ] }, { @@ -1528,7 +1613,8 @@ "cell_type": "markdown", "metadata": {}, "source": [ - "#### 91. How to create a record array from a regular array? (★★★) (suggestion: np.core.records.fromarrays)" + "#### 91. How to create a record array from a regular array? (★★★) \n", + "##### (hint: np.core.records.fromarrays)" ] }, { @@ -1544,7 +1630,8 @@ "cell_type": "markdown", "metadata": {}, "source": [ - "#### 92. Consider a large vector Z, compute Z to the power of 3 using 3 different methods (★★★) (suggestion: np.power, \\*, np.einsum)" + "#### 92. Consider a large vector Z, compute Z to the power of 3 using 3 different methods (★★★) \n", + "##### (hint: np.power, \\*, np.einsum)" ] }, { @@ -1560,7 +1647,8 @@ "cell_type": "markdown", "metadata": {}, "source": [ - "#### 93. Consider two arrays A and B of shape (8,3) and (2,2). How to find rows of A that contain elements of each row of B regardless of the order of the elements in B? (★★★) (suggestion: np.where)" + "#### 93. Consider two arrays A and B of shape (8,3) and (2,2). How to find rows of A that contain elements of each row of B regardless of the order of the elements in B? (★★★) \n", + "##### (hint: np.where)" ] }, { @@ -1592,7 +1680,8 @@ "cell_type": "markdown", "metadata": {}, "source": [ - "#### 95. Convert a vector of ints into a matrix binary representation (★★★) (suggestion: np.unpackbits)" + "#### 95. Convert a vector of ints into a matrix binary representation (★★★) \n", + "##### (hint: np.unpackbits)" ] }, { @@ -1608,7 +1697,8 @@ "cell_type": "markdown", "metadata": {}, "source": [ - "#### 96. Given a two dimensional array, how to extract unique rows? (★★★) (suggestion: np.ascontiguousarray)" + "#### 96. Given a two dimensional array, how to extract unique rows? (★★★) \n", + "##### (hint: np.ascontiguousarray)" ] }, { @@ -1624,7 +1714,8 @@ "cell_type": "markdown", "metadata": {}, "source": [ - "#### 97. Considering 2 vectors A & B, write the einsum equivalent of inner, outer, sum, and mul function (★★★) (suggestion: np.einsum)" + "#### 97. Considering 2 vectors A & B, write the einsum equivalent of inner, outer, sum, and mul function (★★★) \n", + "##### (hint: np.einsum)" ] }, { @@ -1640,7 +1731,8 @@ "cell_type": "markdown", "metadata": {}, "source": [ - "#### 98. Considering a path described by two vectors (X,Y), how to sample it using equidistant samples (★★★)? (suggestion: np.cumsum, np.interp)" + "#### 98. Considering a path described by two vectors (X,Y), how to sample it using equidistant samples (★★★)? \n", + "##### (hint: np.cumsum, np.interp)" ] }, { @@ -1656,7 +1748,8 @@ "cell_type": "markdown", "metadata": {}, "source": [ - "#### 99. Given an integer n and a 2D array X, select from X the rows which can be interpreted as draws from a multinomial distribution with n degrees, i.e., the rows which only contain integers and which sum to n. (★★★) (suggestion: np.logical\\_and.reduce, np.mod)" + "#### 99. Given an integer n and a 2D array X, select from X the rows which can be interpreted as draws from a multinomial distribution with n degrees, i.e., the rows which only contain integers and which sum to n. (★★★) \n", + "##### (hint: np.logical\\_and.reduce, np.mod)" ] }, { @@ -1672,7 +1765,8 @@ "cell_type": "markdown", "metadata": {}, "source": [ - "#### 100. Compute bootstrapped 95% confidence intervals for the mean of a 1D array X (i.e., resample the elements of an array with replacement N times, compute the mean of each sample, and then compute percentiles over the means). (★★★) (suggestion: np.percentile)" + "#### 100. Compute bootstrapped 95% confidence intervals for the mean of a 1D array X (i.e., resample the elements of an array with replacement N times, compute the mean of each sample, and then compute percentiles over the means). (★★★) \n", + "##### (hint: np.percentile)" ] }, { diff --git a/100 Numpy exercises with suggestion.md b/100 Numpy exercises with hint.md similarity index 56% rename from 100 Numpy exercises with suggestion.md rename to 100 Numpy exercises with hint.md index b2a969b..3c10d89 100644 --- a/100 Numpy exercises with suggestion.md +++ b/100 Numpy exercises with hint.md @@ -1,5 +1,5 @@ -# 100 numpy exercises with suggestion +# 100 numpy exercises with hint This is a collection of exercises that have been collected in the numpy mailing list, on stack overflow and in the numpy documentation. I've also created some @@ -10,71 +10,105 @@ those who teach. If you find an error or think you've a better way to solve some of them, feel free to open an issue at -#### 1. Import the numpy package under the name `np` (★☆☆) (suggestion: import … as ..) +#### 1. Import the numpy package under the name `np` (★☆☆) + +##### (hint: import … as ..) -#### 2. Print the numpy version and the configuration (★☆☆) (suggestion: np.\_\_verison\_\_, np.show\_config) +#### 2. Print the numpy version and the configuration (★☆☆) + +##### (hint: np.\_\_verison\_\_, np.show\_config) -#### 3. Create a null vector of size 10 (★☆☆) (suggestion: np.zeros) +#### 3. Create a null vector of size 10 (★☆☆) + +##### (hint: np.zeros) -#### 4. How to find the memory size of any array (★☆☆) (suggestion: size, itemsize) +#### 4. How to find the memory size of any array (★☆☆) + +##### (hint: size, itemsize) -#### 5. How to get the documentation of the numpy add function from the command line? (★☆☆) (suggestion: np.info) +#### 5. How to get the documentation of the numpy add function from the command line? (★☆☆) + +##### (hint: np.info) -#### 6. Create a null vector of size 10 but the fifth value which is 1 (★☆☆) (suggestion: array\[4\]) +#### 6. Create a null vector of size 10 but the fifth value which is 1 (★☆☆) + +##### (hint: array\[4\]) -#### 7. Create a vector with values ranging from 10 to 49 (★☆☆) (suggestion: np.arange) +#### 7. Create a vector with values ranging from 10 to 49 (★☆☆) + +##### (hint: np.arange) -#### 8. Reverse a vector (first element becomes last) (★☆☆) (suggestion: array\[::-1\]) +#### 8. Reverse a vector (first element becomes last) (★☆☆) + +##### (hint: array\[::-1\]) -#### 9. Create a 3x3 matrix with values ranging from 0 to 8 (★☆☆) (suggestion: reshape) +#### 9. Create a 3x3 matrix with values ranging from 0 to 8 (★☆☆) + +##### (hint: reshape) -#### 10. Find indices of non-zero elements from \[1,2,0,0,4,0\] (★☆☆) (suggestion: np.nonzero) +#### 10. Find indices of non-zero elements from \[1,2,0,0,4,0\] (★☆☆) + +##### (hint: np.nonzero) -#### 11. Create a 3x3 identity matrix (★☆☆) (suggestion: np.eye) +#### 11. Create a 3x3 identity matrix (★☆☆) + +##### (hint: np.eye) -#### 12. Create a 3x3x3 array with random values (★☆☆) (suggestion: np.random.random) +#### 12. Create a 3x3x3 array with random values (★☆☆) + +##### (hint: np.random.random) -#### 13. Create a 10x10 array with random values and find the minimum and maximum values (★☆☆) (suggestion: min, max) +#### 13. Create a 10x10 array with random values and find the minimum and maximum values (★☆☆) + +##### (hint: min, max) -#### 14. Create a random vector of size 30 and find the mean value (★☆☆) (suggestion: mean) +#### 14. Create a random vector of size 30 and find the mean value (★☆☆) + +##### (hint: mean) -#### 15. Create a 2d array with 1 on the border and 0 inside (★☆☆) (suggestion: array\[1:-1, 1:-1\]) +#### 15. Create a 2d array with 1 on the border and 0 inside (★☆☆) + +##### (hint: array\[1:-1, 1:-1\]) -#### 16. How to add a border (filled with 0's) around an existing array? (★☆☆) (suggestion: np.pad) +#### 16. How to add a border (filled with 0's) around an existing array? (★☆☆) + +##### (hint: np.pad) -#### 17. What is the result of the following expression? (★☆☆) (suggestion: NaN = not a number, inf = infinity) +#### 17. What is the result of the following expression? (★☆☆) + +##### (hint: NaN = not a number, inf = infinity) ```python @@ -85,39 +119,57 @@ np.nan - np.nan 0.3 == 3 * 0.1 ``` -#### 18. Create a 5x5 matrix with values 1,2,3,4 just below the diagonal (★☆☆) (suggestion: np.diag) +#### 18. Create a 5x5 matrix with values 1,2,3,4 just below the diagonal (★☆☆) + +##### (hint: np.diag) -#### 19. Create a 8x8 matrix and fill it with a checkerboard pattern (★☆☆) (suggestion: array\[::2\]) +#### 19. Create a 8x8 matrix and fill it with a checkerboard pattern (★☆☆) + +##### (hint: array\[::2\]) -#### 20. Consider a (6,7,8) shape array, what is the index (x,y,z) of the 100th element? (suggestion: np.unravel\_index) +#### 20. Consider a (6,7,8) shape array, what is the index (x,y,z) of the 100th element? + +##### (hint: np.unravel\_index) -#### 21. Create a checkerboard 8x8 matrix using the tile function (★☆☆) (suggestion: np.tile) +#### 21. Create a checkerboard 8x8 matrix using the tile function (★☆☆) + +##### (hint: np.tile) -#### 22. Normalize a 5x5 random matrix (★☆☆) (suggestion: (x - min) / (max - min)) +#### 22. Normalize a 5x5 random matrix (★☆☆) + +##### (hint: (x - min) / (max - min)) -#### 23. Create a custom dtype that describes a color as four unsigned bytes (RGBA) (★☆☆) (suggestion: np.dtype) +#### 23. Create a custom dtype that describes a color as four unsigned bytes (RGBA) (★☆☆) + +##### (hint: np.dtype) -#### 24. Multiply a 5x3 matrix by a 3x2 matrix (real matrix product) (★☆☆) (suggestion: np.dot | @) +#### 24. Multiply a 5x3 matrix by a 3x2 matrix (real matrix product) (★☆☆) + +##### (hint: np.dot | @) -#### 25. Given a 1D array, negate all elements which are between 3 and 8, in place. (★☆☆) (suggestion: >, <=) +#### 25. Given a 1D array, negate all elements which are between 3 and 8, in place. (★☆☆) + +##### (hint: >, <=) -#### 26. What is the output of the following script? (★☆☆) (suggestion: np.sum) +#### 26. What is the output of the following script? (★☆☆) + +##### (hint: np.sum) ```python @@ -149,110 +201,162 @@ np.array(0) // np.array(0) np.array([np.nan]).astype(int).astype(float) ``` -#### 29. How to round away from zero a float array ? (★☆☆) (suggestion: np.uniform, np.copysign, np.ceil, np.abs) +#### 29. How to round away from zero a float array ? (★☆☆) + +##### (hint: np.uniform, np.copysign, np.ceil, np.abs) -#### 30. How to find common values between two arrays? (★☆☆) (suggestion: np.intersect1d) +#### 30. How to find common values between two arrays? (★☆☆) + +##### (hint: np.intersect1d) -#### 31. How to ignore all numpy warnings (not recommended)? (★☆☆) (suggestion: np.seterr, np.errstate) +#### 31. How to ignore all numpy warnings (not recommended)? (★☆☆) + +##### (hint: np.seterr, np.errstate) -#### 32. Is the following expressions true? (★☆☆) (suggestion: imaginary number) +#### 32. Is the following expressions true? (★☆☆) + +##### (hint: imaginary number) ```python np.sqrt(-1) == np.emath.sqrt(-1) ``` -#### 33. How to get the dates of yesterday, today and tomorrow? (★☆☆) (suggestion: np.datetime64, np.timedelta64) +#### 33. How to get the dates of yesterday, today and tomorrow? (★☆☆) + +##### (hint: np.datetime64, np.timedelta64) -#### 34. How to get all the dates corresponding to the month of July 2016? (★★☆) (suggestion: np.arange(dtype=datetime64\['D'\])) +#### 34. How to get all the dates corresponding to the month of July 2016? (★★☆) + +##### (hint: np.arange(dtype=datetime64\['D'\])) -#### 35. How to compute ((A+B)\*(-A/2)) in place (without copy)? (★★☆) (suggestion: np.add(out=), np.negative(out=), np.multiply(out=), np.divide(out=)) +#### 35. How to compute ((A+B)\*(-A/2)) in place (without copy)? (★★☆) + +##### (hint: np.add(out=), np.negative(out=), np.multiply(out=), np.divide(out=)) -#### 36. Extract the integer part of a random array using 5 different methods (★★☆) (suggestion: %, np.floor, np.ceil, astype, np.trunc) +#### 36. Extract the integer part of a random array using 5 different methods (★★☆) + +##### (hint: %, np.floor, np.ceil, astype, np.trunc) -#### 37. Create a 5x5 matrix with row values ranging from 0 to 4 (★★☆) (suggestion: np.arange) +#### 37. Create a 5x5 matrix with row values ranging from 0 to 4 (★★☆) + +##### (hint: np.arange) -#### 38. Consider a generator function that generates 10 integers and use it to build an array (★☆☆) (suggestion: np.fromiter) +#### 38. Consider a generator function that generates 10 integers and use it to build an array (★☆☆) + +##### (hint: np.fromiter) -#### 39. Create a vector of size 10 with values ranging from 0 to 1, both excluded (★★☆) (suggestion: np.linespace) +#### 39. Create a vector of size 10 with values ranging from 0 to 1, both excluded (★★☆) + +##### (hint: np.linespace) -#### 40. Create a random vector of size 10 and sort it (★★☆) (suggestion: sort) +#### 40. Create a random vector of size 10 and sort it (★★☆) + +##### (hint: sort) -#### 41. How to sum a small array faster than np.sum? (★★☆) (suggestion: np.add.reduce) +#### 41. How to sum a small array faster than np.sum? (★★☆) + +##### (hint: np.add.reduce) -#### 42. Consider two random array A and B, check if they are equal (★★☆) (suggestion: np.allclose, np.array\_equal) +#### 42. Consider two random array A and B, check if they are equal (★★☆) + +##### (hint: np.allclose, np.array\_equal) -#### 43. Make an array immutable (read-only) (★★☆) (suggestion: flags.writeable) +#### 43. Make an array immutable (read-only) (★★☆) + +##### (hint: flags.writeable) -#### 44. Consider a random 10x2 matrix representing cartesian coordinates, convert them to polar coordinates (★★☆) (suggestion: np.sqrt, np.arctan2) +#### 44. Consider a random 10x2 matrix representing cartesian coordinates, convert them to polar coordinates (★★☆) + +##### (hint: np.sqrt, np.arctan2) -#### 45. Create random vector of size 10 and replace the maximum value by 0 (★★☆) (suggestion: argmax) +#### 45. Create random vector of size 10 and replace the maximum value by 0 (★★☆) + +##### (hint: argmax) -#### 46. Create a structured array with `x` and `y` coordinates covering the \[0,1\]x\[0,1\] area (★★☆) (suggestion: np.meshgrid) +#### 46. Create a structured array with `x` and `y` coordinates covering the \[0,1\]x\[0,1\] area (★★☆) + +##### (hint: np.meshgrid) -#### 47. Given two arrays, X and Y, construct the Cauchy matrix C (Cij =1/(xi - yj)) (suggestion: np.subtract.outer) +#### 47. Given two arrays, X and Y, construct the Cauchy matrix C (Cij =1/(xi - yj)) + +##### (hint: np.subtract.outer) -#### 48. Print the minimum and maximum representable value for each numpy scalar type (★★☆) (suggestion: np.iinfo, np.finfo, eps) +#### 48. Print the minimum and maximum representable value for each numpy scalar type (★★☆) + +##### (hint: np.iinfo, np.finfo, eps) -#### 49. How to print all the values of an array? (★★☆) (suggestion: np.set\_printoptions) +#### 49. How to print all the values of an array? (★★☆) + +##### (hint: np.set\_printoptions) -#### 50. How to find the closest value (to a given scalar) in a vector? (★★☆) (suggestion: argmin) +#### 50. How to find the closest value (to a given scalar) in a vector? (★★☆) + +##### (hint: argmin) -#### 51. Create a structured array representing a position (x,y) and a color (r,g,b) (★★☆) (suggestion: dtype) +#### 51. Create a structured array representing a position (x,y) and a color (r,g,b) (★★☆) + +##### (hint: dtype) -#### 52. Consider a random vector with shape (100,2) representing coordinates, find point by point distances (★★☆) (suggestion: np.atleast\_2d, T, np.sqrt) +#### 52. Consider a random vector with shape (100,2) representing coordinates, find point by point distances (★★☆) + +##### (hint: np.atleast\_2d, T, np.sqrt) -#### 53. How to convert a float (32 bits) array into an integer (32 bits) in place? (suggestion: astype(copy=False)) +#### 53. How to convert a float (32 bits) array into an integer (32 bits) in place? + +##### (hint: astype(copy=False)) -#### 54. How to read the following file? (★★☆) (suggestion: np.genfromtxt) +#### 54. How to read the following file? (★★☆) + +##### (hint: np.genfromtxt) ``` @@ -261,95 +365,141 @@ np.sqrt(-1) == np.emath.sqrt(-1) , , 9,10,11 ``` -#### 55. What is the equivalent of enumerate for numpy arrays? (★★☆) (suggestion: np.ndenumerate, np.ndindex) +#### 55. What is the equivalent of enumerate for numpy arrays? (★★☆) +##### (hint: np.ndenumerate, np.ndindex) -#### 56. Generate a generic 2D Gaussian-like array (★★☆) (suggestion: np.meshgrid, np.exp) +#### 56. Generate a generic 2D Gaussian-like array (★★☆) +##### (hint: np.meshgrid, np.exp) -#### 57. How to randomly place p elements in a 2D array? (★★☆) (suggestion: np.put, np.random.choice) +#### 57. How to randomly place p elements in a 2D array? (★★☆) -#### 58. Subtract the mean of each row of a matrix (★★☆) (suggestion: mean(axis=,keepdims=)) +##### (hint: np.put, np.random.choice) -#### 59. How to sort an array by the nth column? (★★☆) (suggestion: argsort) +#### 58. Subtract the mean of each row of a matrix (★★☆) +##### (hint: mean(axis=,keepdims=)) -#### 60. How to tell if a given 2D array has null columns? (★★☆) (suggestion: any, ~) +#### 59. How to sort an array by the nth column? (★★☆) +##### (hint: argsort) -#### 61. Find the nearest value from a given value in an array (★★☆) (suggestion: np.abs, argmin, flat) +#### 60. How to tell if a given 2D array has null columns? (★★☆) -#### 62. Considering two arrays with shape (1,3) and (3,1), how to compute their sum using an iterator? (★★☆) (suggestion: np.nditer) +##### (hint: any, ~) -#### 63. Create an array class that has a name attribute (★★☆) (suggestion: class method) +#### 61. Find the nearest value from a given value in an array (★★☆) +##### (hint: np.abs, argmin, flat) -#### 64. Consider a given vector, how to add 1 to each element indexed by a second vector (be careful with repeated indices)? (★★★) (suggestion: np.bincount | np.add.at) +#### 62. Considering two arrays with shape (1,3) and (3,1), how to compute their sum using an iterator? (★★☆) +##### (hint: np.nditer) -#### 65. How to accumulate elements of a vector (X) to an array (F) based on an index list (I)? (★★★) (suggestion: np.bincount) +#### 63. Create an array class that has a name attribute (★★☆) -#### 66. Considering a (w,h,3) image of (dtype=ubyte), compute the number of unique colors (★★★) (suggestion: np.unique) +##### (hint: class method) -#### 67. Considering a four dimensions array, how to get sum over the last two axis at once? (★★★) (suggestion: sum(axis=(-2,-1))) +#### 64. Consider a given vector, how to add 1 to each element indexed by a second vector (be careful with repeated indices)? (★★★) +##### (hint: np.bincount | np.add.at) -#### 68. Considering a one-dimensional vector D, how to compute means of subsets of D using a vector S of same size describing subset indices? (★★★) (suggestion: np.bincount) +#### 65. How to accumulate elements of a vector (X) to an array (F) based on an index list (I)? (★★★) +##### (hint: np.bincount) -#### 69. How to get the diagonal of a dot product? (★★★) (suggestion: np.diag) +#### 66. Considering a (w,h,3) image of (dtype=ubyte), compute the number of unique colors (★★★) -#### 70. Consider the vector \[1, 2, 3, 4, 5\], how to build a new vector with 3 consecutive zeros interleaved between each value? (★★★) (suggestion: array\[::4\]) +##### (hint: np.unique) -#### 71. Consider an array of dimension (5,5,3), how to mulitply it by an array with dimensions (5,5)? (★★★) (suggestion: array\[:, :, None\]) +#### 67. Considering a four dimensions array, how to get sum over the last two axis at once? (★★★) +##### (hint: sum(axis=(-2,-1))) -#### 72. How to swap two rows of an array? (★★★) (suggestion: array\[\[\]\] = array\[\[\]\]) +#### 68. Considering a one-dimensional vector D, how to compute means of subsets of D using a vector S of same size describing subset indices? (★★★) +##### (hint: np.bincount) -#### 73. Consider a set of 10 triplets describing 10 triangles (with shared vertices), find the set of unique line segments composing all the triangles (★★★) (suggestion: repeat, np.roll, np.sort, view, np.unique) +#### 69. How to get the diagonal of a dot product? (★★★) -#### 74. Given an array C that is a bincount, how to produce an array A such that np.bincount(A) == C? (★★★) (suggestion: np.repeat) +##### (hint: np.diag) -#### 75. How to compute averages using a sliding window over an array? (★★★) (suggestion: np.cumsum) +#### 70. Consider the vector \[1, 2, 3, 4, 5\], how to build a new vector with 3 consecutive zeros interleaved between each value? (★★★) +##### (hint: array\[::4\]) -#### 76. Consider a one-dimensional array Z, build a two-dimensional array whose first row is (Z\[0\],Z\[1\],Z\[2\]) and each subsequent row is shifted by 1 (last row should be (Z\[-3\],Z\[-2\],Z\[-1\]) (★★★) (suggestion: from numpy.lib import stride\_tricks) +#### 71. Consider an array of dimension (5,5,3), how to mulitply it by an array with dimensions (5,5)? (★★★) +##### (hint: array\[:, :, None\]) -#### 77. How to negate a boolean, or to change the sign of a float inplace? (★★★) (suggestion: np.logical_not, np.negative) + + +#### 72. How to swap two rows of an array? (★★★) + +##### (hint: array\[\[\]\] = array\[\[\]\]) + + + +#### 73. Consider a set of 10 triplets describing 10 triangles (with shared vertices), find the set of unique line segments composing all the triangles (★★★) + +##### (hint: repeat, np.roll, np.sort, view, np.unique) + + + +#### 74. Given an array C that is a bincount, how to produce an array A such that np.bincount(A) == C? (★★★) + +##### (hint: np.repeat) + + + +#### 75. How to compute averages using a sliding window over an array? (★★★) + +##### (hint: np.cumsum) + + + +#### 76. Consider a one-dimensional array Z, build a two-dimensional array whose first row is (Z\[0\],Z\[1\],Z\[2\]) and each subsequent row is shifted by 1 (last row should be (Z\[-3\],Z\[-2\],Z\[-1\]) (★★★) + +##### (hint: from numpy.lib import stride\_tricks) + + + +#### 77. How to negate a boolean, or to change the sign of a float inplace? (★★★) + +##### (hint: np.logical_not, np.negative) @@ -361,35 +511,51 @@ np.sqrt(-1) == np.emath.sqrt(-1) -#### 80. Consider an arbitrary array, write a function that extract a subpart with a fixed shape and centered on a given element (pad with a `fill` value when necessary) (★★★) (suggestion: minimum, maximum) +#### 80. Consider an arbitrary array, write a function that extract a subpart with a fixed shape and centered on a given element (pad with a `fill` value when necessary) (★★★) + +##### (hint: minimum, maximum) -#### 81. Consider an array Z = \[1,2,3,4,5,6,7,8,9,10,11,12,13,14\], how to generate an array R = \[\[1,2,3,4\], \[2,3,4,5\], \[3,4,5,6\], ..., \[11,12,13,14\]\]? (★★★) (suggestion: stride\_tricks.as\_strided) +#### 81. Consider an array Z = \[1,2,3,4,5,6,7,8,9,10,11,12,13,14\], how to generate an array R = \[\[1,2,3,4\], \[2,3,4,5\], \[3,4,5,6\], ..., \[11,12,13,14\]\]? (★★★) + +##### (hint: stride\_tricks.as\_strided) -#### 82. Compute a matrix rank (★★★) (suggestion: np.linalg.svd) +#### 82. Compute a matrix rank (★★★) + +##### (hint: np.linalg.svd) -#### 83. How to find the most frequent value in an array? (suggestion: np.bincount, argmax) +#### 83. How to find the most frequent value in an array? + +##### (hint: np.bincount, argmax) -#### 84. Extract all the contiguous 3x3 blocks from a random 10x10 matrix (★★★) (suggestion: stride\_tricks.as\_strided) +#### 84. Extract all the contiguous 3x3 blocks from a random 10x10 matrix (★★★) + +##### (hint: stride\_tricks.as\_strided) -#### 85. Create a 2D array subclass such that Z\[i,j\] == Z\[j,i\] (★★★) (suggestion: class method) +#### 85. Create a 2D array subclass such that Z\[i,j\] == Z\[j,i\] (★★★) + +##### (hint: class method) -#### 86. Consider a set of p matrices wich shape (n,n) and a set of p vectors with shape (n,1). How to compute the sum of of the p matrix products at once? (result has shape (n,1)) (★★★) (suggestion: np.tensordot) +#### 86. Consider a set of p matrices wich shape (n,n) and a set of p vectors with shape (n,1). How to compute the sum of of the p matrix products at once? (result has shape (n,1)) (★★★) + +##### (hint: np.tensordot) -#### 87. Consider a 16x16 array, how to get the block-sum (block size is 4x4)? (★★★) (suggestion: np.add.reduceat) +#### 87. Consider a 16x16 array, how to get the block-sum (block size is 4x4)? (★★★) + +##### (hint: np.add.reduceat) @@ -397,23 +563,33 @@ np.sqrt(-1) == np.emath.sqrt(-1) -#### 89. How to get the n largest values of an array (★★★) (suggestion: np.argsort | np.argpartition) +#### 89. How to get the n largest values of an array (★★★) + +##### (hint: np.argsort | np.argpartition) -#### 90. Given an arbitrary number of vectors, build the cartesian product (every combinations of every item) (★★★) (suggestion: np.indices) +#### 90. Given an arbitrary number of vectors, build the cartesian product (every combinations of every item) (★★★) + +##### (hint: np.indices) -#### 91. How to create a record array from a regular array? (★★★) (suggestion: np.core.records.fromarrays) +#### 91. How to create a record array from a regular array? (★★★) + +##### (hint: np.core.records.fromarrays) -#### 92. Consider a large vector Z, compute Z to the power of 3 using 3 different methods (★★★) (suggestion: np.power, \*, np.einsum) +#### 92. Consider a large vector Z, compute Z to the power of 3 using 3 different methods (★★★) + +##### (hint: np.power, \*, np.einsum) -#### 93. Consider two arrays A and B of shape (8,3) and (2,2). How to find rows of A that contain elements of each row of B regardless of the order of the elements in B? (★★★) (suggestion: np.where) +#### 93. Consider two arrays A and B of shape (8,3) and (2,2). How to find rows of A that contain elements of each row of B regardless of the order of the elements in B? (★★★) + +##### (hint: np.where) @@ -421,25 +597,37 @@ np.sqrt(-1) == np.emath.sqrt(-1) -#### 95. Convert a vector of ints into a matrix binary representation (★★★) (suggestion: np.unpackbits) +#### 95. Convert a vector of ints into a matrix binary representation (★★★) + +##### (hint: np.unpackbits) -#### 96. Given a two dimensional array, how to extract unique rows? (★★★) (suggestion: np.ascontiguousarray) +#### 96. Given a two dimensional array, how to extract unique rows? (★★★) + +##### (hint: np.ascontiguousarray) -#### 97. Considering 2 vectors A & B, write the einsum equivalent of inner, outer, sum, and mul function (★★★) (suggestion: np.einsum) +#### 97. Considering 2 vectors A & B, write the einsum equivalent of inner, outer, sum, and mul function (★★★) + +##### (hint: np.einsum) -#### 98. Considering a path described by two vectors (X,Y), how to sample it using equidistant samples (★★★)? (suggestion: np.cumsum, np.interp) +#### 98. Considering a path described by two vectors (X,Y), how to sample it using equidistant samples (★★★)? + +##### (hint: np.cumsum, np.interp) -#### 99. Given an integer n and a 2D array X, select from X the rows which can be interpreted as draws from a multinomial distribution with n degrees, i.e., the rows which only contain integers and which sum to n. (★★★) (suggestion: np.logical\_and.reduce, np.mod) +#### 99. Given an integer n and a 2D array X, select from X the rows which can be interpreted as draws from a multinomial distribution with n degrees, i.e., the rows which only contain integers and which sum to n. (★★★) + +##### (hint: np.logical\_and.reduce, np.mod) -#### 100. Compute bootstrapped 95% confidence intervals for the mean of a 1D array X (i.e., resample the elements of an array with replacement N times, compute the mean of each sample, and then compute percentiles over the means). (★★★) (suggestion: np.percentile) +#### 100. Compute bootstrapped 95% confidence intervals for the mean of a 1D array X (i.e., resample the elements of an array with replacement N times, compute the mean of each sample, and then compute percentiles over the means). (★★★) + +##### (hint: np.percentile) From 83d1ac8555fc4017d5ce7bee978b640b15fba0e0 Mon Sep 17 00:00:00 2001 From: matianjun1 Date: Mon, 19 Jun 2017 10:55:30 +0800 Subject: [PATCH 3/4] fix hint to subtitle --- 100 Numpy exercises with hint.ipynb | 188 ++++++++++++++-------------- 100 Numpy exercises with hint.md | 186 +++++++++++++-------------- 2 files changed, 187 insertions(+), 187 deletions(-) diff --git a/100 Numpy exercises with hint.ipynb b/100 Numpy exercises with hint.ipynb index d9dd849..d1ea964 100644 --- a/100 Numpy exercises with hint.ipynb +++ b/100 Numpy exercises with hint.ipynb @@ -17,7 +17,7 @@ "metadata": {}, "source": [ "#### 1. Import the numpy package under the name `np` (★☆☆) \n", - "##### (hint: import … as ..)" + "(**hint**: import ... as ..)" ] }, { @@ -34,7 +34,7 @@ "metadata": {}, "source": [ "#### 2. Print the numpy version and the configuration (★☆☆) \n", - "##### (hint: np.\\_\\_verison\\_\\_, np.show\\_config)" + "(**hint**: np.\\_\\_verison\\_\\_, np.show\\_config)" ] }, { @@ -51,7 +51,7 @@ "metadata": {}, "source": [ "#### 3. Create a null vector of size 10 (★☆☆) \n", - "##### (hint: np.zeros)" + "(**hint**: np.zeros)" ] }, { @@ -68,7 +68,7 @@ "metadata": {}, "source": [ "#### 4. How to find the memory size of any array (★☆☆) \n", - "##### (hint: size, itemsize)" + "(**hint**: size, itemsize)" ] }, { @@ -85,7 +85,7 @@ "metadata": {}, "source": [ "#### 5. How to get the documentation of the numpy add function from the command line? (★☆☆) \n", - "##### (hint: np.info)" + "(**hint**: np.info)" ] }, { @@ -102,7 +102,7 @@ "metadata": {}, "source": [ "#### 6. Create a null vector of size 10 but the fifth value which is 1 (★☆☆) \n", - "##### (hint: array\\[4\\])" + "(**hint**: array\\[4\\])" ] }, { @@ -119,7 +119,7 @@ "metadata": {}, "source": [ "#### 7. Create a vector with values ranging from 10 to 49 (★☆☆) \n", - "##### (hint: np.arange)" + "(**hint**: np.arange)" ] }, { @@ -136,7 +136,7 @@ "metadata": {}, "source": [ "#### 8. Reverse a vector (first element becomes last) (★☆☆) \n", - "##### (hint: array\\[::-1\\])" + "(**hint**: array\\[::-1\\])" ] }, { @@ -153,7 +153,7 @@ "metadata": {}, "source": [ "#### 9. Create a 3x3 matrix with values ranging from 0 to 8 (★☆☆) \n", - "##### (hint: reshape)" + "(**hint**: reshape)" ] }, { @@ -170,7 +170,7 @@ "metadata": {}, "source": [ "#### 10. Find indices of non-zero elements from \\[1,2,0,0,4,0\\] (★☆☆) \n", - "##### (hint: np.nonzero)" + "(**hint**: np.nonzero)" ] }, { @@ -187,7 +187,7 @@ "metadata": {}, "source": [ "#### 11. Create a 3x3 identity matrix (★☆☆) \n", - "##### (hint: np.eye)" + "(**hint**: np.eye)" ] }, { @@ -204,7 +204,7 @@ "metadata": {}, "source": [ "#### 12. Create a 3x3x3 array with random values (★☆☆) \n", - "##### (hint: np.random.random)" + "(**hint**: np.random.random)" ] }, { @@ -221,7 +221,7 @@ "metadata": {}, "source": [ "#### 13. Create a 10x10 array with random values and find the minimum and maximum values (★☆☆) \n", - "##### (hint: min, max)" + "(**hint**: min, max)" ] }, { @@ -238,7 +238,7 @@ "metadata": {}, "source": [ "#### 14. Create a random vector of size 30 and find the mean value (★☆☆) \n", - "##### (hint: mean)" + "(**hint**: mean)" ] }, { @@ -255,7 +255,7 @@ "metadata": {}, "source": [ "#### 15. Create a 2d array with 1 on the border and 0 inside (★☆☆) \n", - "##### (hint: array\\[1:-1, 1:-1\\])" + "(**hint**: array\\[1:-1, 1:-1\\])" ] }, { @@ -272,7 +272,7 @@ "metadata": {}, "source": [ "#### 16. How to add a border (filled with 0's) around an existing array? (★☆☆) \n", - "##### (hint: np.pad)" + "(**hint**: np.pad)" ] }, { @@ -289,7 +289,7 @@ "metadata": {}, "source": [ "#### 17. What is the result of the following expression? (★☆☆) \n", - "##### (hint: NaN = not a number, inf = infinity)" + "(**hint**: NaN = not a number, inf = infinity)" ] }, { @@ -319,7 +319,7 @@ "metadata": {}, "source": [ "#### 18. Create a 5x5 matrix with values 1,2,3,4 just below the diagonal (★☆☆) \n", - "##### (hint: np.diag)" + "(**hint**: np.diag)" ] }, { @@ -336,7 +336,7 @@ "metadata": {}, "source": [ "#### 19. Create a 8x8 matrix and fill it with a checkerboard pattern (★☆☆) \n", - "##### (hint: array\\[::2\\])" + "(**hint**: array\\[::2\\])" ] }, { @@ -353,7 +353,7 @@ "metadata": {}, "source": [ "#### 20. Consider a (6,7,8) shape array, what is the index (x,y,z) of the 100th element? \n", - "##### (hint: np.unravel_index)" + "(**hint**: np.unravel_index)" ] }, { @@ -370,7 +370,7 @@ "metadata": {}, "source": [ "#### 21. Create a checkerboard 8x8 matrix using the tile function (★☆☆) \n", - "##### (hint: np.tile)" + "(**hint**: np.tile)" ] }, { @@ -387,7 +387,7 @@ "metadata": {}, "source": [ "#### 22. Normalize a 5x5 random matrix (★☆☆) \n", - "##### (hint: (x - min) / (max - min))" + "(**hint**: (x - min) / (max - min))" ] }, { @@ -404,7 +404,7 @@ "metadata": {}, "source": [ "#### 23. Create a custom dtype that describes a color as four unsigned bytes (RGBA) (★☆☆) \n", - "##### (hint: np.dtype)" + "(**hint**: np.dtype)" ] }, { @@ -421,7 +421,7 @@ "metadata": {}, "source": [ "#### 24. Multiply a 5x3 matrix by a 3x2 matrix (real matrix product) (★☆☆) \n", - "##### (hint: np.dot | @)" + "(**hint**: np.dot | @)" ] }, { @@ -438,7 +438,7 @@ "metadata": {}, "source": [ "#### 25. Given a 1D array, negate all elements which are between 3 and 8, in place. (★☆☆) \n", - "##### (hint: >, <=)" + "(**hint**: >, <=)" ] }, { @@ -455,7 +455,7 @@ "metadata": {}, "source": [ "#### 26. What is the output of the following script? (★☆☆) \n", - "##### (hint: np.sum)" + "(**hint**: np.sum)" ] }, { @@ -542,7 +542,7 @@ "metadata": {}, "source": [ "#### 29. How to round away from zero a float array ? (★☆☆) \n", - "##### (hint: np.uniform, np.copysign, np.ceil, np.abs)" + "(**hint**: np.uniform, np.copysign, np.ceil, np.abs)" ] }, { @@ -559,7 +559,7 @@ "metadata": {}, "source": [ "#### 30. How to find common values between two arrays? (★☆☆) \n", - "##### (hint: np.intersect1d)" + "(**hint**: np.intersect1d)" ] }, { @@ -576,7 +576,7 @@ "metadata": {}, "source": [ "#### 31. How to ignore all numpy warnings (not recommended)? (★☆☆) \n", - "##### (hint: np.seterr, np.errstate)" + "(**hint**: np.seterr, np.errstate)" ] }, { @@ -593,7 +593,7 @@ "metadata": {}, "source": [ "#### 32. Is the following expressions true? (★☆☆) \n", - "##### (hint: imaginary number)" + "(**hint**: imaginary number)" ] }, { @@ -619,7 +619,7 @@ "metadata": {}, "source": [ "#### 33. How to get the dates of yesterday, today and tomorrow? (★☆☆) \n", - "##### (hint: np.datetime64, np.timedelta64)" + "(**hint**: np.datetime64, np.timedelta64)" ] }, { @@ -636,7 +636,7 @@ "metadata": {}, "source": [ "#### 34. How to get all the dates corresponding to the month of July 2016? (★★☆) \n", - "##### (hint: np.arange(dtype=datetime64\\['D'\\]))" + "(**hint**: np.arange(dtype=datetime64\\['D'\\]))" ] }, { @@ -653,7 +653,7 @@ "metadata": {}, "source": [ "#### 35. How to compute ((A+B)\\*(-A/2)) in place (without copy)? (★★☆) \n", - "##### (hint: np.add(out=), np.negative(out=), np.multiply(out=), np.divide(out=))" + "(**hint**: np.add(out=), np.negative(out=), np.multiply(out=), np.divide(out=))" ] }, { @@ -670,7 +670,7 @@ "metadata": {}, "source": [ "#### 36. Extract the integer part of a random array using 5 different methods (★★☆) \n", - "##### (hint: %, np.floor, np.ceil, astype, np.trunc)" + "(**hint**: %, np.floor, np.ceil, astype, np.trunc)" ] }, { @@ -687,7 +687,7 @@ "metadata": {}, "source": [ "#### 37. Create a 5x5 matrix with row values ranging from 0 to 4 (★★☆) \n", - "##### (hint: np.arange)" + "(**hint**: np.arange)" ] }, { @@ -704,7 +704,7 @@ "metadata": {}, "source": [ "#### 38. Consider a generator function that generates 10 integers and use it to build an array (★☆☆) \n", - "##### (hint: np.fromiter)" + "(**hint**: np.fromiter)" ] }, { @@ -721,7 +721,7 @@ "metadata": {}, "source": [ "#### 39. Create a vector of size 10 with values ranging from 0 to 1, both excluded (★★☆) \n", - "##### (hint: np.linespace)" + "(**hint**: np.linespace)" ] }, { @@ -738,7 +738,7 @@ "metadata": {}, "source": [ "#### 40. Create a random vector of size 10 and sort it (★★☆) \n", - "##### (hint: sort)" + "(**hint**: sort)" ] }, { @@ -755,7 +755,7 @@ "metadata": {}, "source": [ "#### 41. How to sum a small array faster than np.sum? (★★☆) \n", - "##### (hint: np.add.reduce)" + "(**hint**: np.add.reduce)" ] }, { @@ -772,7 +772,7 @@ "metadata": {}, "source": [ "#### 42. Consider two random array A and B, check if they are equal (★★☆) \n", - "##### (hint: np.allclose, np.array\\_equal)" + "(**hint**: np.allclose, np.array\\_equal)" ] }, { @@ -789,7 +789,7 @@ "metadata": {}, "source": [ "#### 43. Make an array immutable (read-only) (★★☆) \n", - "##### (hint: flags.writeable)" + "(**hint**: flags.writeable)" ] }, { @@ -806,7 +806,7 @@ "metadata": {}, "source": [ "#### 44. Consider a random 10x2 matrix representing cartesian coordinates, convert them to polar coordinates (★★☆) \n", - "##### (hint: np.sqrt, np.arctan2)" + "(**hint**: np.sqrt, np.arctan2)" ] }, { @@ -823,7 +823,7 @@ "metadata": {}, "source": [ "#### 45. Create random vector of size 10 and replace the maximum value by 0 (★★☆) \n", - "##### (hint: argmax)" + "(**hint**: argmax)" ] }, { @@ -840,7 +840,7 @@ "metadata": {}, "source": [ "#### 46. Create a structured array with `x` and `y` coordinates covering the \\[0,1\\]x\\[0,1\\] area (★★☆) \n", - "##### (hint: np.meshgrid)" + "(**hint**: np.meshgrid)" ] }, { @@ -857,7 +857,7 @@ "metadata": {}, "source": [ "#### 47. Given two arrays, X and Y, construct the Cauchy matrix C (Cij =1/(xi - yj)) \n", - "##### (hint: np.subtract.outer)" + "(**hint**: np.subtract.outer)" ] }, { @@ -874,7 +874,7 @@ "metadata": {}, "source": [ "#### 48. Print the minimum and maximum representable value for each numpy scalar type (★★☆) \n", - "##### (hint: np.iinfo, np.finfo, eps)" + "(**hint**: np.iinfo, np.finfo, eps)" ] }, { @@ -891,7 +891,7 @@ "metadata": {}, "source": [ "#### 49. How to print all the values of an array? (★★☆) \n", - "##### (hint: np.set\\_printoptions)" + "(**hint**: np.set\\_printoptions)" ] }, { @@ -908,7 +908,7 @@ "metadata": {}, "source": [ "#### 50. How to find the closest value (to a given scalar) in a vector? (★★☆) \n", - "##### (hint: argmin)" + "(**hint**: argmin)" ] }, { @@ -925,7 +925,7 @@ "metadata": {}, "source": [ "#### 51. Create a structured array representing a position (x,y) and a color (r,g,b) (★★☆) \n", - "##### (hint: dtype)" + "(**hint**: dtype)" ] }, { @@ -942,7 +942,7 @@ "metadata": {}, "source": [ "#### 52. Consider a random vector with shape (100,2) representing coordinates, find point by point distances (★★☆) \n", - "##### (hint: np.atleast\\_2d, T, np.sqrt)" + "(**hint**: np.atleast\\_2d, T, np.sqrt)" ] }, { @@ -959,7 +959,7 @@ "metadata": {}, "source": [ "#### 53. How to convert a float (32 bits) array into an integer (32 bits) in place? \n", - "##### (hint: astype(copy=False))" + "(**hint**: astype(copy=False))" ] }, { @@ -976,7 +976,7 @@ "metadata": {}, "source": [ "#### 54. How to read the following file? (★★☆) \n", - "##### (hint: np.genfromtxt)" + "(**hint**: np.genfromtxt)" ] }, { @@ -1004,7 +1004,7 @@ "metadata": {}, "source": [ "#### 55. What is the equivalent of enumerate for numpy arrays? (★★☆) \n", - "##### (hint: np.ndenumerate, np.ndindex)" + "(**hint**: np.ndenumerate, np.ndindex)" ] }, { @@ -1021,7 +1021,7 @@ "metadata": {}, "source": [ "#### 56. Generate a generic 2D Gaussian-like array (★★☆) \n", - "##### (hint: np.meshgrid, np.exp)" + "(**hint**: np.meshgrid, np.exp)" ] }, { @@ -1038,7 +1038,7 @@ "metadata": {}, "source": [ "#### 57. How to randomly place p elements in a 2D array? (★★☆) \n", - "##### (hint: np.put, np.random.choice)" + "(**hint**: np.put, np.random.choice)" ] }, { @@ -1055,7 +1055,7 @@ "metadata": {}, "source": [ "#### 58. Subtract the mean of each row of a matrix (★★☆) \n", - "##### (hint: mean(axis=,keepdims=))" + "(**hint**: mean(axis=,keepdims=))" ] }, { @@ -1072,7 +1072,7 @@ "metadata": {}, "source": [ "#### 59. How to sort an array by the nth column? (★★☆) \n", - "##### (hint: argsort)" + "(**hint**: argsort)" ] }, { @@ -1089,7 +1089,7 @@ "metadata": {}, "source": [ "#### 60. How to tell if a given 2D array has null columns? (★★☆) \n", - "##### (hint: any, ~)" + "(**hint**: any, ~)" ] }, { @@ -1106,7 +1106,7 @@ "metadata": {}, "source": [ "#### 61. Find the nearest value from a given value in an array (★★☆) \n", - "##### (hint: np.abs, argmin, flat)" + "(**hint**: np.abs, argmin, flat)" ] }, { @@ -1123,7 +1123,7 @@ "metadata": {}, "source": [ "#### 62. Considering two arrays with shape (1,3) and (3,1), how to compute their sum using an iterator? (★★☆) \n", - "##### (hint: np.nditer)" + "(**hint**: np.nditer)" ] }, { @@ -1140,7 +1140,7 @@ "metadata": {}, "source": [ "#### 63. Create an array class that has a name attribute (★★☆) \n", - "##### (hint: class method)" + "(**hint**: class method)" ] }, { @@ -1157,7 +1157,7 @@ "metadata": {}, "source": [ "#### 64. Consider a given vector, how to add 1 to each element indexed by a second vector (be careful with repeated indices)? (★★★) \n", - "##### (hint: np.bincount | np.add.at)" + "(**hint**: np.bincount | np.add.at)" ] }, { @@ -1174,7 +1174,7 @@ "metadata": {}, "source": [ "#### 65. How to accumulate elements of a vector (X) to an array (F) based on an index list (I)? (★★★) \n", - "##### (hint: np.bincount)" + "(**hint**: np.bincount)" ] }, { @@ -1191,7 +1191,7 @@ "metadata": {}, "source": [ "#### 66. Considering a (w,h,3) image of (dtype=ubyte), compute the number of unique colors (★★★) \n", - "##### (hint: np.unique)" + "(**hint**: np.unique)" ] }, { @@ -1208,7 +1208,7 @@ "metadata": {}, "source": [ "#### 67. Considering a four dimensions array, how to get sum over the last two axis at once? (★★★) \n", - "##### (hint: sum(axis=(-2,-1)))" + "(**hint**: sum(axis=(-2,-1)))" ] }, { @@ -1225,7 +1225,7 @@ "metadata": {}, "source": [ "#### 68. Considering a one-dimensional vector D, how to compute means of subsets of D using a vector S of same size describing subset indices? (★★★) \n", - "##### (hint: np.bincount)" + "(**hint**: np.bincount)" ] }, { @@ -1242,7 +1242,7 @@ "metadata": {}, "source": [ "#### 69. How to get the diagonal of a dot product? (★★★) \n", - "##### (hint: np.diag)" + "(**hint**: np.diag)" ] }, { @@ -1259,7 +1259,7 @@ "metadata": {}, "source": [ "#### 70. Consider the vector \\[1, 2, 3, 4, 5\\], how to build a new vector with 3 consecutive zeros interleaved between each value? (★★★) \n", - "##### (hint: array\\[::4\\])" + "(**hint**: array\\[::4\\])" ] }, { @@ -1276,7 +1276,7 @@ "metadata": {}, "source": [ "#### 71. Consider an array of dimension (5,5,3), how to mulitply it by an array with dimensions (5,5)? (★★★) \n", - "##### (hint: array\\[:, :, None\\])" + "(**hint**: array\\[:, :, None\\])" ] }, { @@ -1293,7 +1293,7 @@ "metadata": {}, "source": [ "#### 72. How to swap two rows of an array? (★★★) \n", - "##### (hint: array\\[\\[\\]\\] = array\\[\\[\\]\\])" + "(**hint**: array\\[\\[\\]\\] = array\\[\\[\\]\\])" ] }, { @@ -1310,7 +1310,7 @@ "metadata": {}, "source": [ "#### 73. Consider a set of 10 triplets describing 10 triangles (with shared vertices), find the set of unique line segments composing all the triangles (★★★) \n", - "##### (hint: repeat, np.roll, np.sort, view, np.unique)" + "(**hint**: repeat, np.roll, np.sort, view, np.unique)" ] }, { @@ -1327,7 +1327,7 @@ "metadata": {}, "source": [ "#### 74. Given an array C that is a bincount, how to produce an array A such that np.bincount(A) == C? (★★★) \n", - "##### (hint: np.repeat)" + "(**hint**: np.repeat)" ] }, { @@ -1344,7 +1344,7 @@ "metadata": {}, "source": [ "#### 75. How to compute averages using a sliding window over an array? (★★★) \n", - "##### (hint: np.cumsum)" + "(**hint**: np.cumsum)" ] }, { @@ -1361,7 +1361,7 @@ "metadata": {}, "source": [ "#### 76. Consider a one-dimensional array Z, build a two-dimensional array whose first row is (Z\\[0\\],Z\\[1\\],Z\\[2\\]) and each subsequent row is shifted by 1 (last row should be (Z\\[-3\\],Z\\[-2\\],Z\\[-1\\]) (★★★) \n", - "##### (hint: from numpy.lib import stride_tricks)" + "(**hint**: from numpy.lib import stride_tricks)" ] }, { @@ -1378,7 +1378,7 @@ "metadata": {}, "source": [ "#### 77. How to negate a boolean, or to change the sign of a float inplace? (★★★) \n", - "##### (hint: np.logical_not, np.negative)" + "(**hint**: np.logical_not, np.negative)" ] }, { @@ -1427,7 +1427,7 @@ "metadata": {}, "source": [ "#### 80. Consider an arbitrary array, write a function that extract a subpart with a fixed shape and centered on a given element (pad with a `fill` value when necessary) (★★★) \n", - "##### (hint: minimum, maximum)" + "(**hint**: minimum, maximum)" ] }, { @@ -1444,7 +1444,7 @@ "metadata": {}, "source": [ "#### 81. Consider an array Z = \\[1,2,3,4,5,6,7,8,9,10,11,12,13,14\\], how to generate an array R = \\[\\[1,2,3,4\\], \\[2,3,4,5\\], \\[3,4,5,6\\], ..., \\[11,12,13,14\\]\\]? (★★★) \n", - "##### (hint: stride\\_tricks.as\\_strided)" + "(**hint**: stride\\_tricks.as\\_strided)" ] }, { @@ -1461,7 +1461,7 @@ "metadata": {}, "source": [ "#### 82. Compute a matrix rank (★★★) \n", - "##### (hint: np.linalg.svd) (suggestion: np.linalg.svd)" + "(**hint**: np.linalg.svd) (suggestion: np.linalg.svd)" ] }, { @@ -1478,7 +1478,7 @@ "metadata": {}, "source": [ "#### 83. How to find the most frequent value in an array? \n", - "##### (hint: np.bincount, argmax)" + "(**hint**: np.bincount, argmax)" ] }, { @@ -1495,7 +1495,7 @@ "metadata": {}, "source": [ "#### 84. Extract all the contiguous 3x3 blocks from a random 10x10 matrix (★★★) \n", - "##### (hint: stride\\_tricks.as\\_strided)" + "(**hint**: stride\\_tricks.as\\_strided)" ] }, { @@ -1512,7 +1512,7 @@ "metadata": {}, "source": [ "#### 85. Create a 2D array subclass such that Z\\[i,j\\] == Z\\[j,i\\] (★★★) \n", - "##### (hint: class method)" + "(**hint**: class method)" ] }, { @@ -1529,7 +1529,7 @@ "metadata": {}, "source": [ "#### 86. Consider a set of p matrices wich shape (n,n) and a set of p vectors with shape (n,1). How to compute the sum of of the p matrix products at once? (result has shape (n,1)) (★★★) \n", - "##### (hint: np.tensordot)" + "(**hint**: np.tensordot)" ] }, { @@ -1546,7 +1546,7 @@ "metadata": {}, "source": [ "#### 87. Consider a 16x16 array, how to get the block-sum (block size is 4x4)? (★★★) \n", - "##### (hint: np.add.reduceat)" + "(**hint**: np.add.reduceat)" ] }, { @@ -1579,7 +1579,7 @@ "metadata": {}, "source": [ "#### 89. How to get the n largest values of an array (★★★) \n", - "##### (hint: np.argsort | np.argpartition)" + "(**hint**: np.argsort | np.argpartition)" ] }, { @@ -1596,7 +1596,7 @@ "metadata": {}, "source": [ "#### 90. Given an arbitrary number of vectors, build the cartesian product (every combinations of every item) (★★★) \n", - "##### (hint: np.indices)" + "(**hint**: np.indices)" ] }, { @@ -1614,7 +1614,7 @@ "metadata": {}, "source": [ "#### 91. How to create a record array from a regular array? (★★★) \n", - "##### (hint: np.core.records.fromarrays)" + "(**hint**: np.core.records.fromarrays)" ] }, { @@ -1631,7 +1631,7 @@ "metadata": {}, "source": [ "#### 92. Consider a large vector Z, compute Z to the power of 3 using 3 different methods (★★★) \n", - "##### (hint: np.power, \\*, np.einsum)" + "(**hint**: np.power, \\*, np.einsum)" ] }, { @@ -1648,7 +1648,7 @@ "metadata": {}, "source": [ "#### 93. Consider two arrays A and B of shape (8,3) and (2,2). How to find rows of A that contain elements of each row of B regardless of the order of the elements in B? (★★★) \n", - "##### (hint: np.where)" + "(**hint**: np.where)" ] }, { @@ -1681,7 +1681,7 @@ "metadata": {}, "source": [ "#### 95. Convert a vector of ints into a matrix binary representation (★★★) \n", - "##### (hint: np.unpackbits)" + "(**hint**: np.unpackbits)" ] }, { @@ -1698,7 +1698,7 @@ "metadata": {}, "source": [ "#### 96. Given a two dimensional array, how to extract unique rows? (★★★) \n", - "##### (hint: np.ascontiguousarray)" + "(**hint**: np.ascontiguousarray)" ] }, { @@ -1715,7 +1715,7 @@ "metadata": {}, "source": [ "#### 97. Considering 2 vectors A & B, write the einsum equivalent of inner, outer, sum, and mul function (★★★) \n", - "##### (hint: np.einsum)" + "(**hint**: np.einsum)" ] }, { @@ -1732,7 +1732,7 @@ "metadata": {}, "source": [ "#### 98. Considering a path described by two vectors (X,Y), how to sample it using equidistant samples (★★★)? \n", - "##### (hint: np.cumsum, np.interp)" + "(**hint**: np.cumsum, np.interp)" ] }, { @@ -1749,7 +1749,7 @@ "metadata": {}, "source": [ "#### 99. Given an integer n and a 2D array X, select from X the rows which can be interpreted as draws from a multinomial distribution with n degrees, i.e., the rows which only contain integers and which sum to n. (★★★) \n", - "##### (hint: np.logical\\_and.reduce, np.mod)" + "(**hint**: np.logical\\_and.reduce, np.mod)" ] }, { @@ -1766,7 +1766,7 @@ "metadata": {}, "source": [ "#### 100. Compute bootstrapped 95% confidence intervals for the mean of a 1D array X (i.e., resample the elements of an array with replacement N times, compute the mean of each sample, and then compute percentiles over the means). (★★★) \n", - "##### (hint: np.percentile)" + "(**hint**: np.percentile)" ] }, { diff --git a/100 Numpy exercises with hint.md b/100 Numpy exercises with hint.md index 3c10d89..cd92748 100644 --- a/100 Numpy exercises with hint.md +++ b/100 Numpy exercises with hint.md @@ -12,103 +12,103 @@ free to open an issue at #### 1. Import the numpy package under the name `np` (★☆☆) -##### (hint: import … as ..) +(**hint**: import … as ..) #### 2. Print the numpy version and the configuration (★☆☆) -##### (hint: np.\_\_verison\_\_, np.show\_config) +(**hint**: np.\_\_verison\_\_, np.show\_config) #### 3. Create a null vector of size 10 (★☆☆) -##### (hint: np.zeros) +(**hint**: np.zeros) #### 4. How to find the memory size of any array (★☆☆) -##### (hint: size, itemsize) +(**hint**: size, itemsize) #### 5. How to get the documentation of the numpy add function from the command line? (★☆☆) -##### (hint: np.info) +(**hint**: np.info) #### 6. Create a null vector of size 10 but the fifth value which is 1 (★☆☆) -##### (hint: array\[4\]) +(**hint**: array\[4\]) #### 7. Create a vector with values ranging from 10 to 49 (★☆☆) -##### (hint: np.arange) +(**hint**: np.arange) #### 8. Reverse a vector (first element becomes last) (★☆☆) -##### (hint: array\[::-1\]) +(**hint**: array\[::-1\]) #### 9. Create a 3x3 matrix with values ranging from 0 to 8 (★☆☆) -##### (hint: reshape) +(**hint**: reshape) #### 10. Find indices of non-zero elements from \[1,2,0,0,4,0\] (★☆☆) -##### (hint: np.nonzero) +(**hint**: np.nonzero) #### 11. Create a 3x3 identity matrix (★☆☆) -##### (hint: np.eye) +(**hint**: np.eye) #### 12. Create a 3x3x3 array with random values (★☆☆) -##### (hint: np.random.random) +(**hint**: np.random.random) #### 13. Create a 10x10 array with random values and find the minimum and maximum values (★☆☆) -##### (hint: min, max) +(**hint**: min, max) #### 14. Create a random vector of size 30 and find the mean value (★☆☆) -##### (hint: mean) +(**hint**: mean) #### 15. Create a 2d array with 1 on the border and 0 inside (★☆☆) -##### (hint: array\[1:-1, 1:-1\]) +(**hint**: array\[1:-1, 1:-1\]) #### 16. How to add a border (filled with 0's) around an existing array? (★☆☆) -##### (hint: np.pad) +(**hint**: np.pad) #### 17. What is the result of the following expression? (★☆☆) -##### (hint: NaN = not a number, inf = infinity) +(**hint**: NaN = not a number, inf = infinity) ```python @@ -121,55 +121,55 @@ np.nan - np.nan #### 18. Create a 5x5 matrix with values 1,2,3,4 just below the diagonal (★☆☆) -##### (hint: np.diag) +(**hint**: np.diag) #### 19. Create a 8x8 matrix and fill it with a checkerboard pattern (★☆☆) -##### (hint: array\[::2\]) +(**hint**: array\[::2\]) #### 20. Consider a (6,7,8) shape array, what is the index (x,y,z) of the 100th element? -##### (hint: np.unravel\_index) +(**hint**: np.unravel\_index) #### 21. Create a checkerboard 8x8 matrix using the tile function (★☆☆) -##### (hint: np.tile) +(**hint**: np.tile) #### 22. Normalize a 5x5 random matrix (★☆☆) -##### (hint: (x - min) / (max - min)) +(**hint**: (x - min) / (max - min)) #### 23. Create a custom dtype that describes a color as four unsigned bytes (RGBA) (★☆☆) -##### (hint: np.dtype) +(**hint**: np.dtype) #### 24. Multiply a 5x3 matrix by a 3x2 matrix (real matrix product) (★☆☆) -##### (hint: np.dot | @) +(**hint**: np.dot | @) #### 25. Given a 1D array, negate all elements which are between 3 and 8, in place. (★☆☆) -##### (hint: >, <=) +(**hint**: >, <=) #### 26. What is the output of the following script? (★☆☆) -##### (hint: np.sum) +(**hint**: np.sum) ```python @@ -203,25 +203,25 @@ np.array([np.nan]).astype(int).astype(float) #### 29. How to round away from zero a float array ? (★☆☆) -##### (hint: np.uniform, np.copysign, np.ceil, np.abs) +(**hint**: np.uniform, np.copysign, np.ceil, np.abs) #### 30. How to find common values between two arrays? (★☆☆) -##### (hint: np.intersect1d) +(**hint**: np.intersect1d) #### 31. How to ignore all numpy warnings (not recommended)? (★☆☆) -##### (hint: np.seterr, np.errstate) +(**hint**: np.seterr, np.errstate) #### 32. Is the following expressions true? (★☆☆) -##### (hint: imaginary number) +(**hint**: imaginary number) ```python @@ -230,85 +230,85 @@ np.sqrt(-1) == np.emath.sqrt(-1) #### 33. How to get the dates of yesterday, today and tomorrow? (★☆☆) -##### (hint: np.datetime64, np.timedelta64) +(**hint**: np.datetime64, np.timedelta64) #### 34. How to get all the dates corresponding to the month of July 2016? (★★☆) -##### (hint: np.arange(dtype=datetime64\['D'\])) +(**hint**: np.arange(dtype=datetime64\['D'\])) #### 35. How to compute ((A+B)\*(-A/2)) in place (without copy)? (★★☆) -##### (hint: np.add(out=), np.negative(out=), np.multiply(out=), np.divide(out=)) +(**hint**: np.add(out=), np.negative(out=), np.multiply(out=), np.divide(out=)) #### 36. Extract the integer part of a random array using 5 different methods (★★☆) -##### (hint: %, np.floor, np.ceil, astype, np.trunc) +(**hint**: %, np.floor, np.ceil, astype, np.trunc) #### 37. Create a 5x5 matrix with row values ranging from 0 to 4 (★★☆) -##### (hint: np.arange) +(**hint**: np.arange) #### 38. Consider a generator function that generates 10 integers and use it to build an array (★☆☆) -##### (hint: np.fromiter) +(**hint**: np.fromiter) #### 39. Create a vector of size 10 with values ranging from 0 to 1, both excluded (★★☆) -##### (hint: np.linespace) +(**hint**: np.linespace) #### 40. Create a random vector of size 10 and sort it (★★☆) -##### (hint: sort) +(**hint**: sort) #### 41. How to sum a small array faster than np.sum? (★★☆) -##### (hint: np.add.reduce) +(**hint**: np.add.reduce) #### 42. Consider two random array A and B, check if they are equal (★★☆) -##### (hint: np.allclose, np.array\_equal) +(**hint**: np.allclose, np.array\_equal) #### 43. Make an array immutable (read-only) (★★☆) -##### (hint: flags.writeable) +(**hint**: flags.writeable) #### 44. Consider a random 10x2 matrix representing cartesian coordinates, convert them to polar coordinates (★★☆) -##### (hint: np.sqrt, np.arctan2) +(**hint**: np.sqrt, np.arctan2) #### 45. Create random vector of size 10 and replace the maximum value by 0 (★★☆) -##### (hint: argmax) +(**hint**: argmax) #### 46. Create a structured array with `x` and `y` coordinates covering the \[0,1\]x\[0,1\] area (★★☆) -##### (hint: np.meshgrid) +(**hint**: np.meshgrid) @@ -320,43 +320,43 @@ np.sqrt(-1) == np.emath.sqrt(-1) #### 48. Print the minimum and maximum representable value for each numpy scalar type (★★☆) -##### (hint: np.iinfo, np.finfo, eps) +(**hint**: np.iinfo, np.finfo, eps) #### 49. How to print all the values of an array? (★★☆) -##### (hint: np.set\_printoptions) +(**hint**: np.set\_printoptions) #### 50. How to find the closest value (to a given scalar) in a vector? (★★☆) -##### (hint: argmin) +(**hint**: argmin) #### 51. Create a structured array representing a position (x,y) and a color (r,g,b) (★★☆) -##### (hint: dtype) +(**hint**: dtype) #### 52. Consider a random vector with shape (100,2) representing coordinates, find point by point distances (★★☆) -##### (hint: np.atleast\_2d, T, np.sqrt) +(**hint**: np.atleast\_2d, T, np.sqrt) #### 53. How to convert a float (32 bits) array into an integer (32 bits) in place? -##### (hint: astype(copy=False)) +(**hint**: astype(copy=False)) #### 54. How to read the following file? (★★☆) -##### (hint: np.genfromtxt) +(**hint**: np.genfromtxt) ``` @@ -367,139 +367,139 @@ np.sqrt(-1) == np.emath.sqrt(-1) #### 55. What is the equivalent of enumerate for numpy arrays? (★★☆) -##### (hint: np.ndenumerate, np.ndindex) +(**hint**: np.ndenumerate, np.ndindex) #### 56. Generate a generic 2D Gaussian-like array (★★☆) -##### (hint: np.meshgrid, np.exp) +(**hint**: np.meshgrid, np.exp) #### 57. How to randomly place p elements in a 2D array? (★★☆) -##### (hint: np.put, np.random.choice) +(**hint**: np.put, np.random.choice) #### 58. Subtract the mean of each row of a matrix (★★☆) -##### (hint: mean(axis=,keepdims=)) +(**hint**: mean(axis=,keepdims=)) #### 59. How to sort an array by the nth column? (★★☆) -##### (hint: argsort) +(**hint**: argsort) #### 60. How to tell if a given 2D array has null columns? (★★☆) -##### (hint: any, ~) +(**hint**: any, ~) #### 61. Find the nearest value from a given value in an array (★★☆) -##### (hint: np.abs, argmin, flat) +(**hint**: np.abs, argmin, flat) #### 62. Considering two arrays with shape (1,3) and (3,1), how to compute their sum using an iterator? (★★☆) -##### (hint: np.nditer) +(**hint**: np.nditer) #### 63. Create an array class that has a name attribute (★★☆) -##### (hint: class method) +(**hint**: class method) #### 64. Consider a given vector, how to add 1 to each element indexed by a second vector (be careful with repeated indices)? (★★★) -##### (hint: np.bincount | np.add.at) +(**hint**: np.bincount | np.add.at) #### 65. How to accumulate elements of a vector (X) to an array (F) based on an index list (I)? (★★★) -##### (hint: np.bincount) +(**hint**: np.bincount) #### 66. Considering a (w,h,3) image of (dtype=ubyte), compute the number of unique colors (★★★) -##### (hint: np.unique) +(**hint**: np.unique) #### 67. Considering a four dimensions array, how to get sum over the last two axis at once? (★★★) -##### (hint: sum(axis=(-2,-1))) +(**hint**: sum(axis=(-2,-1))) #### 68. Considering a one-dimensional vector D, how to compute means of subsets of D using a vector S of same size describing subset indices? (★★★) -##### (hint: np.bincount) +(**hint**: np.bincount) #### 69. How to get the diagonal of a dot product? (★★★) -##### (hint: np.diag) +(**hint**: np.diag) #### 70. Consider the vector \[1, 2, 3, 4, 5\], how to build a new vector with 3 consecutive zeros interleaved between each value? (★★★) -##### (hint: array\[::4\]) +(**hint**: array\[::4\]) #### 71. Consider an array of dimension (5,5,3), how to mulitply it by an array with dimensions (5,5)? (★★★) -##### (hint: array\[:, :, None\]) +(**hint**: array\[:, :, None\]) #### 72. How to swap two rows of an array? (★★★) -##### (hint: array\[\[\]\] = array\[\[\]\]) +(**hint**: array\[\[\]\] = array\[\[\]\]) #### 73. Consider a set of 10 triplets describing 10 triangles (with shared vertices), find the set of unique line segments composing all the triangles (★★★) -##### (hint: repeat, np.roll, np.sort, view, np.unique) +(**hint**: repeat, np.roll, np.sort, view, np.unique) #### 74. Given an array C that is a bincount, how to produce an array A such that np.bincount(A) == C? (★★★) -##### (hint: np.repeat) +(**hint**: np.repeat) #### 75. How to compute averages using a sliding window over an array? (★★★) -##### (hint: np.cumsum) +(**hint**: np.cumsum) #### 76. Consider a one-dimensional array Z, build a two-dimensional array whose first row is (Z\[0\],Z\[1\],Z\[2\]) and each subsequent row is shifted by 1 (last row should be (Z\[-3\],Z\[-2\],Z\[-1\]) (★★★) -##### (hint: from numpy.lib import stride\_tricks) +(**hint**: from numpy.lib import stride\_tricks) #### 77. How to negate a boolean, or to change the sign of a float inplace? (★★★) -##### (hint: np.logical_not, np.negative) +(**hint**: np.logical_not, np.negative) @@ -513,49 +513,49 @@ np.sqrt(-1) == np.emath.sqrt(-1) #### 80. Consider an arbitrary array, write a function that extract a subpart with a fixed shape and centered on a given element (pad with a `fill` value when necessary) (★★★) -##### (hint: minimum, maximum) +(**hint**: minimum, maximum) #### 81. Consider an array Z = \[1,2,3,4,5,6,7,8,9,10,11,12,13,14\], how to generate an array R = \[\[1,2,3,4\], \[2,3,4,5\], \[3,4,5,6\], ..., \[11,12,13,14\]\]? (★★★) -##### (hint: stride\_tricks.as\_strided) +(**hint**: stride\_tricks.as\_strided) #### 82. Compute a matrix rank (★★★) -##### (hint: np.linalg.svd) +(**hint**: np.linalg.svd) #### 83. How to find the most frequent value in an array? -##### (hint: np.bincount, argmax) +(**hint**: np.bincount, argmax) #### 84. Extract all the contiguous 3x3 blocks from a random 10x10 matrix (★★★) -##### (hint: stride\_tricks.as\_strided) +(**hint**: stride\_tricks.as\_strided) #### 85. Create a 2D array subclass such that Z\[i,j\] == Z\[j,i\] (★★★) -##### (hint: class method) +(**hint**: class method) #### 86. Consider a set of p matrices wich shape (n,n) and a set of p vectors with shape (n,1). How to compute the sum of of the p matrix products at once? (result has shape (n,1)) (★★★) -##### (hint: np.tensordot) +(**hint**: np.tensordot) #### 87. Consider a 16x16 array, how to get the block-sum (block size is 4x4)? (★★★) -##### (hint: np.add.reduceat) +(**hint**: np.add.reduceat) @@ -565,31 +565,31 @@ np.sqrt(-1) == np.emath.sqrt(-1) #### 89. How to get the n largest values of an array (★★★) -##### (hint: np.argsort | np.argpartition) +(**hint**: np.argsort | np.argpartition) #### 90. Given an arbitrary number of vectors, build the cartesian product (every combinations of every item) (★★★) -##### (hint: np.indices) +(**hint**: np.indices) #### 91. How to create a record array from a regular array? (★★★) -##### (hint: np.core.records.fromarrays) +(**hint**: np.core.records.fromarrays) #### 92. Consider a large vector Z, compute Z to the power of 3 using 3 different methods (★★★) -##### (hint: np.power, \*, np.einsum) +(**hint**: np.power, \*, np.einsum) #### 93. Consider two arrays A and B of shape (8,3) and (2,2). How to find rows of A that contain elements of each row of B regardless of the order of the elements in B? (★★★) -##### (hint: np.where) +(**hint**: np.where) @@ -599,35 +599,35 @@ np.sqrt(-1) == np.emath.sqrt(-1) #### 95. Convert a vector of ints into a matrix binary representation (★★★) -##### (hint: np.unpackbits) +(**hint**: np.unpackbits) #### 96. Given a two dimensional array, how to extract unique rows? (★★★) -##### (hint: np.ascontiguousarray) +(**hint**: np.ascontiguousarray) #### 97. Considering 2 vectors A & B, write the einsum equivalent of inner, outer, sum, and mul function (★★★) -##### (hint: np.einsum) +(**hint**: np.einsum) #### 98. Considering a path described by two vectors (X,Y), how to sample it using equidistant samples (★★★)? -##### (hint: np.cumsum, np.interp) +(**hint**: np.cumsum, np.interp) #### 99. Given an integer n and a 2D array X, select from X the rows which can be interpreted as draws from a multinomial distribution with n degrees, i.e., the rows which only contain integers and which sum to n. (★★★) -##### (hint: np.logical\_and.reduce, np.mod) +(**hint**: np.logical\_and.reduce, np.mod) #### 100. Compute bootstrapped 95% confidence intervals for the mean of a 1D array X (i.e., resample the elements of an array with replacement N times, compute the mean of each sample, and then compute percentiles over the means). (★★★) -##### (hint: np.percentile) +(**hint**: np.percentile) From 3db0975407b5fbcc4c0b2a718c2a8c7ec3c8668d Mon Sep 17 00:00:00 2001 From: matianjun1 Date: Mon, 19 Jun 2017 13:52:11 +0800 Subject: [PATCH 4/4] fix some small signal error --- 100 Numpy exercises with hint.ipynb | 2 +- 100 Numpy exercises with hint.md | 2 +- 2 files changed, 2 insertions(+), 2 deletions(-) diff --git a/100 Numpy exercises with hint.ipynb b/100 Numpy exercises with hint.ipynb index d1ea964..cc629f2 100644 --- a/100 Numpy exercises with hint.ipynb +++ b/100 Numpy exercises with hint.ipynb @@ -17,7 +17,7 @@ "metadata": {}, "source": [ "#### 1. Import the numpy package under the name `np` (★☆☆) \n", - "(**hint**: import ... as ..)" + "(**hint**: import … as …)" ] }, { diff --git a/100 Numpy exercises with hint.md b/100 Numpy exercises with hint.md index cd92748..1bfc5d1 100644 --- a/100 Numpy exercises with hint.md +++ b/100 Numpy exercises with hint.md @@ -12,7 +12,7 @@ free to open an issue at #### 1. Import the numpy package under the name `np` (★☆☆) -(**hint**: import … as ..) +(**hint**: import … as …)