daviddoji/numpy-100
1
0
Fork 0
Code Issues Pull Requests Packages Projects Releases Wiki Activity

fix hint to subtitle

Browse Source
This commit is contained in:
matianjun1
2017-06-19 10:55:30 +08:00
parent 453fa9fa14
commit 83d1ac8555
2 changed files with 187 additions and 187 deletions
Download Patch File Download Diff File Expand all files Collapse all files

188
100 Numpy exercises with hint.ipynb
View File

@@ -17,7 +17,7 @@
"metadata": {}, "metadata": {},
"source": [ "source": [
"#### 1. Import the numpy package under the name `np` (★☆☆) \n", "#### 1. Import the numpy package under the name `np` (★☆☆) \n",
"##### (hint: import … as ..)" "(**hint**: import ... as ..)"
] ]
}, },
{ {
@@ -34,7 +34,7 @@
"metadata": {}, "metadata": {},
"source": [ "source": [
"#### 2. Print the numpy version and the configuration (★☆☆) \n", "#### 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": {}, "metadata": {},
"source": [ "source": [
"#### 3. Create a null vector of size 10 (★☆☆) \n", "#### 3. Create a null vector of size 10 (★☆☆) \n",
"##### (hint: np.zeros)" "(**hint**: np.zeros)"
] ]
}, },
{ {
@@ -68,7 +68,7 @@
"metadata": {}, "metadata": {},
"source": [ "source": [
"#### 4. How to find the memory size of any array (★☆☆) \n", "#### 4. How to find the memory size of any array (★☆☆) \n",
"##### (hint: size, itemsize)" "(**hint**: size, itemsize)"
] ]
}, },
{ {
@@ -85,7 +85,7 @@
"metadata": {}, "metadata": {},
"source": [ "source": [
"#### 5. How to get the documentation of the numpy add function from the command line? (★☆☆) \n", "#### 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": {}, "metadata": {},
"source": [ "source": [
"#### 6. Create a null vector of size 10 but the fifth value which is 1 (★☆☆) \n", "#### 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": {}, "metadata": {},
"source": [ "source": [
"#### 7. Create a vector with values ranging from 10 to 49 (★☆☆) \n", "#### 7. Create a vector with values ranging from 10 to 49 (★☆☆) \n",
"##### (hint: np.arange)" "(**hint**: np.arange)"
] ]
}, },
{ {
@@ -136,7 +136,7 @@
"metadata": {}, "metadata": {},
"source": [ "source": [
"#### 8. Reverse a vector (first element becomes last) (★☆☆) \n", "#### 8. Reverse a vector (first element becomes last) (★☆☆) \n",
"##### (hint: array\\[::-1\\])" "(**hint**: array\\[::-1\\])"
] ]
}, },
{ {
@@ -153,7 +153,7 @@
"metadata": {}, "metadata": {},
"source": [ "source": [
"#### 9. Create a 3x3 matrix with values ranging from 0 to 8 (★☆☆) \n", "#### 9. Create a 3x3 matrix with values ranging from 0 to 8 (★☆☆) \n",
"##### (hint: reshape)" "(**hint**: reshape)"
] ]
}, },
{ {
@@ -170,7 +170,7 @@
"metadata": {}, "metadata": {},
"source": [ "source": [
"#### 10. Find indices of non-zero elements from \\[1,2,0,0,4,0\\] (★☆☆) \n", "#### 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": {}, "metadata": {},
"source": [ "source": [
"#### 11. Create a 3x3 identity matrix (★☆☆) \n", "#### 11. Create a 3x3 identity matrix (★☆☆) \n",
"##### (hint: np.eye)" "(**hint**: np.eye)"
] ]
}, },
{ {
@@ -204,7 +204,7 @@
"metadata": {}, "metadata": {},
"source": [ "source": [
"#### 12. Create a 3x3x3 array with random values (★☆☆) \n", "#### 12. Create a 3x3x3 array with random values (★☆☆) \n",
"##### (hint: np.random.random)" "(**hint**: np.random.random)"
] ]
}, },
{ {
@@ -221,7 +221,7 @@
"metadata": {}, "metadata": {},
"source": [ "source": [
"#### 13. Create a 10x10 array with random values and find the minimum and maximum values (★☆☆) \n", "#### 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": {}, "metadata": {},
"source": [ "source": [
"#### 14. Create a random vector of size 30 and find the mean value (★☆☆) \n", "#### 14. Create a random vector of size 30 and find the mean value (★☆☆) \n",
"##### (hint: mean)" "(**hint**: mean)"
] ]
}, },
{ {
@@ -255,7 +255,7 @@
"metadata": {}, "metadata": {},
"source": [ "source": [
"#### 15. Create a 2d array with 1 on the border and 0 inside (★☆☆) \n", "#### 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": {}, "metadata": {},
"source": [ "source": [
"#### 16. How to add a border (filled with 0's) around an existing array? (★☆☆) \n", "#### 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": {}, "metadata": {},
"source": [ "source": [
"#### 17. What is the result of the following expression? (★☆☆) \n", "#### 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": {}, "metadata": {},
"source": [ "source": [
"#### 18. Create a 5x5 matrix with values 1,2,3,4 just below the diagonal (★☆☆) \n", "#### 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": {}, "metadata": {},
"source": [ "source": [
"#### 19. Create a 8x8 matrix and fill it with a checkerboard pattern (★☆☆) \n", "#### 19. Create a 8x8 matrix and fill it with a checkerboard pattern (★☆☆) \n",
"##### (hint: array\\[::2\\])" "(**hint**: array\\[::2\\])"
] ]
}, },
{ {
@@ -353,7 +353,7 @@
"metadata": {}, "metadata": {},
"source": [ "source": [
"#### 20. Consider a (6,7,8) shape array, what is the index (x,y,z) of the 100th element? \n", "#### 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": {}, "metadata": {},
"source": [ "source": [
"#### 21. Create a checkerboard 8x8 matrix using the tile function (★☆☆) \n", "#### 21. Create a checkerboard 8x8 matrix using the tile function (★☆☆) \n",
"##### (hint: np.tile)" "(**hint**: np.tile)"
] ]
}, },
{ {
@@ -387,7 +387,7 @@
"metadata": {}, "metadata": {},
"source": [ "source": [
"#### 22. Normalize a 5x5 random matrix (★☆☆) \n", "#### 22. Normalize a 5x5 random matrix (★☆☆) \n",
"##### (hint: (x - min) / (max - min))" "(**hint**: (x - min) / (max - min))"
] ]
}, },
{ {
@@ -404,7 +404,7 @@
"metadata": {}, "metadata": {},
"source": [ "source": [
"#### 23. Create a custom dtype that describes a color as four unsigned bytes (RGBA) (★☆☆) \n", "#### 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": {}, "metadata": {},
"source": [ "source": [
"#### 24. Multiply a 5x3 matrix by a 3x2 matrix (real matrix product) (★☆☆) \n", "#### 24. Multiply a 5x3 matrix by a 3x2 matrix (real matrix product) (★☆☆) \n",
"##### (hint: np.dot | @)" "(**hint**: np.dot | @)"
] ]
}, },
{ {
@@ -438,7 +438,7 @@
"metadata": {}, "metadata": {},
"source": [ "source": [
"#### 25. Given a 1D array, negate all elements which are between 3 and 8, in place. (★☆☆) \n", "#### 25. Given a 1D array, negate all elements which are between 3 and 8, in place. (★☆☆) \n",
"##### (hint: >, <=)" "(**hint**: >, <=)"
] ]
}, },
{ {
@@ -455,7 +455,7 @@
"metadata": {}, "metadata": {},
"source": [ "source": [
"#### 26. What is the output of the following script? (★☆☆) \n", "#### 26. What is the output of the following script? (★☆☆) \n",
"##### (hint: np.sum)" "(**hint**: np.sum)"
] ]
}, },
{ {
@@ -542,7 +542,7 @@
"metadata": {}, "metadata": {},
"source": [ "source": [
"#### 29. How to round away from zero a float array ? (★☆☆) \n", "#### 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": {}, "metadata": {},
"source": [ "source": [
"#### 30. How to find common values between two arrays? (★☆☆) \n", "#### 30. How to find common values between two arrays? (★☆☆) \n",
"##### (hint: np.intersect1d)" "(**hint**: np.intersect1d)"
] ]
}, },
{ {
@@ -576,7 +576,7 @@
"metadata": {}, "metadata": {},
"source": [ "source": [
"#### 31. How to ignore all numpy warnings (not recommended)? (★☆☆) \n", "#### 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": {}, "metadata": {},
"source": [ "source": [
"#### 32. Is the following expressions true? (★☆☆) \n", "#### 32. Is the following expressions true? (★☆☆) \n",
"##### (hint: imaginary number)" "(**hint**: imaginary number)"
] ]
}, },
{ {
@@ -619,7 +619,7 @@
"metadata": {}, "metadata": {},
"source": [ "source": [
"#### 33. How to get the dates of yesterday, today and tomorrow? (★☆☆) \n", "#### 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": {}, "metadata": {},
"source": [ "source": [
"#### 34. How to get all the dates corresponding to the month of July 2016? (★★☆) \n", "#### 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": {}, "metadata": {},
"source": [ "source": [
"#### 35. How to compute ((A+B)\\*(-A/2)) in place (without copy)? (★★☆) \n", "#### 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": {}, "metadata": {},
"source": [ "source": [
"#### 36. Extract the integer part of a random array using 5 different methods (★★☆) \n", "#### 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": {}, "metadata": {},
"source": [ "source": [
"#### 37. Create a 5x5 matrix with row values ranging from 0 to 4 (★★☆) \n", "#### 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": {}, "metadata": {},
"source": [ "source": [
"#### 38. Consider a generator function that generates 10 integers and use it to build an array (★☆☆) \n", "#### 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": {}, "metadata": {},
"source": [ "source": [
"#### 39. Create a vector of size 10 with values ranging from 0 to 1, both excluded (★★☆) \n", "#### 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": {}, "metadata": {},
"source": [ "source": [
"#### 40. Create a random vector of size 10 and sort it (★★☆) \n", "#### 40. Create a random vector of size 10 and sort it (★★☆) \n",
"##### (hint: sort)" "(**hint**: sort)"
] ]
}, },
{ {
@@ -755,7 +755,7 @@
"metadata": {}, "metadata": {},
"source": [ "source": [
"#### 41. How to sum a small array faster than np.sum? (★★☆) \n", "#### 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": {}, "metadata": {},
"source": [ "source": [
"#### 42. Consider two random array A and B, check if they are equal (★★☆) \n", "#### 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": {}, "metadata": {},
"source": [ "source": [
"#### 43. Make an array immutable (read-only) (★★☆) \n", "#### 43. Make an array immutable (read-only) (★★☆) \n",
"##### (hint: flags.writeable)" "(**hint**: flags.writeable)"
] ]
}, },
{ {
@@ -806,7 +806,7 @@
"metadata": {}, "metadata": {},
"source": [ "source": [
"#### 44. Consider a random 10x2 matrix representing cartesian coordinates, convert them to polar coordinates (★★☆) \n", "#### 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": {}, "metadata": {},
"source": [ "source": [
"#### 45. Create random vector of size 10 and replace the maximum value by 0 (★★☆) \n", "#### 45. Create random vector of size 10 and replace the maximum value by 0 (★★☆) \n",
"##### (hint: argmax)" "(**hint**: argmax)"
] ]
}, },
{ {
@@ -840,7 +840,7 @@
"metadata": {}, "metadata": {},
"source": [ "source": [
"#### 46. Create a structured array with `x` and `y` coordinates covering the \\[0,1\\]x\\[0,1\\] area (★★☆) \n", "#### 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": {}, "metadata": {},
"source": [ "source": [
"#### 47. Given two arrays, X and Y, construct the Cauchy matrix C (Cij =1/(xi - yj)) \n", "#### 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": {}, "metadata": {},
"source": [ "source": [
"#### 48. Print the minimum and maximum representable value for each numpy scalar type (★★☆) \n", "#### 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": {}, "metadata": {},
"source": [ "source": [
"#### 49. How to print all the values of an array? (★★☆) \n", "#### 49. How to print all the values of an array? (★★☆) \n",
"##### (hint: np.set\\_printoptions)" "(**hint**: np.set\\_printoptions)"
] ]
}, },
{ {
@@ -908,7 +908,7 @@
"metadata": {}, "metadata": {},
"source": [ "source": [
"#### 50. How to find the closest value (to a given scalar) in a vector? (★★☆) \n", "#### 50. How to find the closest value (to a given scalar) in a vector? (★★☆) \n",
"##### (hint: argmin)" "(**hint**: argmin)"
] ]
}, },
{ {
@@ -925,7 +925,7 @@
"metadata": {}, "metadata": {},
"source": [ "source": [
"#### 51. Create a structured array representing a position (x,y) and a color (r,g,b) (★★☆) \n", "#### 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": {}, "metadata": {},
"source": [ "source": [
"#### 52. Consider a random vector with shape (100,2) representing coordinates, find point by point distances (★★☆) \n", "#### 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": {}, "metadata": {},
"source": [ "source": [
"#### 53. How to convert a float (32 bits) array into an integer (32 bits) in place? \n", "#### 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": {}, "metadata": {},
"source": [ "source": [
"#### 54. How to read the following file? (★★☆) \n", "#### 54. How to read the following file? (★★☆) \n",
"##### (hint: np.genfromtxt)" "(**hint**: np.genfromtxt)"
] ]
}, },
{ {
@@ -1004,7 +1004,7 @@
"metadata": {}, "metadata": {},
"source": [ "source": [
"#### 55. What is the equivalent of enumerate for numpy arrays? (★★☆) \n", "#### 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": {}, "metadata": {},
"source": [ "source": [
"#### 56. Generate a generic 2D Gaussian-like array (★★☆) \n", "#### 56. Generate a generic 2D Gaussian-like array (★★☆) \n",
"##### (hint: np.meshgrid, np.exp)" "(**hint**: np.meshgrid, np.exp)"
] ]
}, },
{ {
@@ -1038,7 +1038,7 @@
"metadata": {}, "metadata": {},
"source": [ "source": [
"#### 57. How to randomly place p elements in a 2D array? (★★☆) \n", "#### 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": {}, "metadata": {},
"source": [ "source": [
"#### 58. Subtract the mean of each row of a matrix (★★☆) \n", "#### 58. Subtract the mean of each row of a matrix (★★☆) \n",
"##### (hint: mean(axis=,keepdims=))" "(**hint**: mean(axis=,keepdims=))"
] ]
}, },
{ {
@@ -1072,7 +1072,7 @@
"metadata": {}, "metadata": {},
"source": [ "source": [
"#### 59. How to sort an array by the nth column? (★★☆) \n", "#### 59. How to sort an array by the nth column? (★★☆) \n",
"##### (hint: argsort)" "(**hint**: argsort)"
] ]
}, },
{ {
@@ -1089,7 +1089,7 @@
"metadata": {}, "metadata": {},
"source": [ "source": [
"#### 60. How to tell if a given 2D array has null columns? (★★☆) \n", "#### 60. How to tell if a given 2D array has null columns? (★★☆) \n",
"##### (hint: any, ~)" "(**hint**: any, ~)"
] ]
}, },
{ {
@@ -1106,7 +1106,7 @@
"metadata": {}, "metadata": {},
"source": [ "source": [
"#### 61. Find the nearest value from a given value in an array (★★☆) \n", "#### 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": {}, "metadata": {},
"source": [ "source": [
"#### 62. Considering two arrays with shape (1,3) and (3,1), how to compute their sum using an iterator? (★★☆) \n", "#### 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": {}, "metadata": {},
"source": [ "source": [
"#### 63. Create an array class that has a name attribute (★★☆) \n", "#### 63. Create an array class that has a name attribute (★★☆) \n",
"##### (hint: class method)" "(**hint**: class method)"
] ]
}, },
{ {
@@ -1157,7 +1157,7 @@
"metadata": {}, "metadata": {},
"source": [ "source": [
"#### 64. Consider a given vector, how to add 1 to each element indexed by a second vector (be careful with repeated indices)? (★★★) \n", "#### 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": {}, "metadata": {},
"source": [ "source": [
"#### 65. How to accumulate elements of a vector (X) to an array (F) based on an index list (I)? (★★★) \n", "#### 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": {}, "metadata": {},
"source": [ "source": [
"#### 66. Considering a (w,h,3) image of (dtype=ubyte), compute the number of unique colors (★★★) \n", "#### 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": {}, "metadata": {},
"source": [ "source": [
"#### 67. Considering a four dimensions array, how to get sum over the last two axis at once? (★★★) \n", "#### 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": {}, "metadata": {},
"source": [ "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", "#### 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": {}, "metadata": {},
"source": [ "source": [
"#### 69. How to get the diagonal of a dot product? (★★★) \n", "#### 69. How to get the diagonal of a dot product? (★★★) \n",
"##### (hint: np.diag)" "(**hint**: np.diag)"
] ]
}, },
{ {
@@ -1259,7 +1259,7 @@
"metadata": {}, "metadata": {},
"source": [ "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", "#### 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": {}, "metadata": {},
"source": [ "source": [
"#### 71. Consider an array of dimension (5,5,3), how to mulitply it by an array with dimensions (5,5)? (★★★) \n", "#### 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": {}, "metadata": {},
"source": [ "source": [
"#### 72. How to swap two rows of an array? (★★★) \n", "#### 72. How to swap two rows of an array? (★★★) \n",
"##### (hint: array\\[\\[\\]\\] = array\\[\\[\\]\\])" "(**hint**: array\\[\\[\\]\\] = array\\[\\[\\]\\])"
] ]
}, },
{ {
@@ -1310,7 +1310,7 @@
"metadata": {}, "metadata": {},
"source": [ "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", "#### 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": {}, "metadata": {},
"source": [ "source": [
"#### 74. Given an array C that is a bincount, how to produce an array A such that np.bincount(A) == C? (★★★) \n", "#### 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": {}, "metadata": {},
"source": [ "source": [
"#### 75. How to compute averages using a sliding window over an array? (★★★) \n", "#### 75. How to compute averages using a sliding window over an array? (★★★) \n",
"##### (hint: np.cumsum)" "(**hint**: np.cumsum)"
] ]
}, },
{ {
@@ -1361,7 +1361,7 @@
"metadata": {}, "metadata": {},
"source": [ "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", "#### 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": {}, "metadata": {},
"source": [ "source": [
"#### 77. How to negate a boolean, or to change the sign of a float inplace? (★★★) \n", "#### 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": {}, "metadata": {},
"source": [ "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", "#### 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": {}, "metadata": {},
"source": [ "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", "#### 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": {}, "metadata": {},
"source": [ "source": [
"#### 82. Compute a matrix rank (★★★) \n", "#### 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": {}, "metadata": {},
"source": [ "source": [
"#### 83. How to find the most frequent value in an array? \n", "#### 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": {}, "metadata": {},
"source": [ "source": [
"#### 84. Extract all the contiguous 3x3 blocks from a random 10x10 matrix (★★★) \n", "#### 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": {}, "metadata": {},
"source": [ "source": [
"#### 85. Create a 2D array subclass such that Z\\[i,j\\] == Z\\[j,i\\] (★★★) \n", "#### 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": {}, "metadata": {},
"source": [ "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", "#### 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": {}, "metadata": {},
"source": [ "source": [
"#### 87. Consider a 16x16 array, how to get the block-sum (block size is 4x4)? (★★★) \n", "#### 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": {}, "metadata": {},
"source": [ "source": [
"#### 89. How to get the n largest values of an array (★★★) \n", "#### 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": {}, "metadata": {},
"source": [ "source": [
"#### 90. Given an arbitrary number of vectors, build the cartesian product (every combinations of every item) (★★★) \n", "#### 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": {}, "metadata": {},
"source": [ "source": [
"#### 91. How to create a record array from a regular array? (★★★) \n", "#### 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": {}, "metadata": {},
"source": [ "source": [
"#### 92. Consider a large vector Z, compute Z to the power of 3 using 3 different methods (★★★) \n", "#### 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": {}, "metadata": {},
"source": [ "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", "#### 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": {}, "metadata": {},
"source": [ "source": [
"#### 95. Convert a vector of ints into a matrix binary representation (★★★) \n", "#### 95. Convert a vector of ints into a matrix binary representation (★★★) \n",
"##### (hint: np.unpackbits)" "(**hint**: np.unpackbits)"
] ]
}, },
{ {
@@ -1698,7 +1698,7 @@
"metadata": {}, "metadata": {},
"source": [ "source": [
"#### 96. Given a two dimensional array, how to extract unique rows? (★★★) \n", "#### 96. Given a two dimensional array, how to extract unique rows? (★★★) \n",
"##### (hint: np.ascontiguousarray)" "(**hint**: np.ascontiguousarray)"
] ]
}, },
{ {
@@ -1715,7 +1715,7 @@
"metadata": {}, "metadata": {},
"source": [ "source": [
"#### 97. Considering 2 vectors A & B, write the einsum equivalent of inner, outer, sum, and mul function (★★★) \n", "#### 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": {}, "metadata": {},
"source": [ "source": [
"#### 98. Considering a path described by two vectors (X,Y), how to sample it using equidistant samples (★★★)? \n", "#### 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": {}, "metadata": {},
"source": [ "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", "#### 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": {}, "metadata": {},
"source": [ "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", "#### 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)"
] ]
}, },
{ {

186
100 Numpy exercises with hint.md
View File

@@ -12,103 +12,103 @@ free to open an issue at <https://github.com/rougier/numpy-100>
#### 1. Import the numpy package under the name `np` (★☆☆) #### 1. Import the numpy package under the name `np` (★☆☆)
##### (hint: import … as ..) (**hint**: import … as ..)
#### 2. Print the numpy version and the configuration (★☆☆) #### 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 (★☆☆) #### 3. Create a null vector of size 10 (★☆☆)
##### (hint: np.zeros) (**hint**: np.zeros)
#### 4. How to find the memory size of any array (★☆☆) #### 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? (★☆☆) #### 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 (★☆☆) #### 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 (★☆☆) #### 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) (★☆☆) #### 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 (★☆☆) #### 9. Create a 3x3 matrix with values ranging from 0 to 8 (★☆☆)
##### (hint: reshape) (**hint**: reshape)
#### 10. Find indices of non-zero elements from \[1,2,0,0,4,0\] (★☆☆) #### 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 (★☆☆) #### 11. Create a 3x3 identity matrix (★☆☆)
##### (hint: np.eye) (**hint**: np.eye)
#### 12. Create a 3x3x3 array with random values (★☆☆) #### 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 (★☆☆) #### 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 (★☆☆) #### 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 (★☆☆) #### 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? (★☆☆) #### 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? (★☆☆) #### 17. What is the result of the following expression? (★☆☆)
##### (hint: NaN = not a number, inf = infinity) (**hint**: NaN = not a number, inf = infinity)
```python ```python
@@ -121,55 +121,55 @@ np.nan - np.nan
#### 18. Create a 5x5 matrix with values 1,2,3,4 just below the diagonal (★☆☆) #### 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 (★☆☆) #### 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? #### 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 (★☆☆) #### 21. Create a checkerboard 8x8 matrix using the tile function (★☆☆)
##### (hint: np.tile) (**hint**: np.tile)
#### 22. Normalize a 5x5 random matrix (★☆☆) #### 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) (★☆☆) #### 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) (★☆☆) #### 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. (★☆☆) #### 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? (★☆☆) #### 26. What is the output of the following script? (★☆☆)
##### (hint: np.sum) (**hint**: np.sum)
```python ```python
@@ -203,25 +203,25 @@ np.array([np.nan]).astype(int).astype(float)
#### 29. How to round away from zero a float array ? (★☆☆) #### 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? (★☆☆) #### 30. How to find common values between two arrays? (★☆☆)
##### (hint: np.intersect1d) (**hint**: np.intersect1d)
#### 31. How to ignore all numpy warnings (not recommended)? (★☆☆) #### 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? (★☆☆) #### 32. Is the following expressions true? (★☆☆)
##### (hint: imaginary number) (**hint**: imaginary number)
```python ```python
@@ -230,85 +230,85 @@ np.sqrt(-1) == np.emath.sqrt(-1)
#### 33. How to get the dates of yesterday, today and tomorrow? (★☆☆) #### 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? (★★☆) #### 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)? (★★☆) #### 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 (★★☆) #### 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 (★★☆) #### 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 (★☆☆) #### 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 (★★☆) #### 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 (★★☆) #### 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? (★★☆) #### 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 (★★☆) #### 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) (★★☆) #### 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 (★★☆) #### 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 (★★☆) #### 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 (★★☆) #### 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 (★★☆) #### 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? (★★☆) #### 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? (★★☆) #### 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) (★★☆) #### 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 (★★☆) #### 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? #### 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? (★★☆) #### 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? (★★☆) #### 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 (★★☆) #### 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? (★★☆) #### 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 (★★☆) #### 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? (★★☆) #### 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? (★★☆) #### 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 (★★☆) #### 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? (★★☆) #### 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 (★★☆) #### 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)? (★★★) #### 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)? (★★★) #### 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 (★★★) #### 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? (★★★) #### 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? (★★★) #### 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? (★★★) #### 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? (★★★) #### 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)? (★★★) #### 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? (★★★) #### 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 (★★★) #### 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? (★★★) #### 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? (★★★) #### 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\[-1\]) (★★★) #### 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? (★★★) #### 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) (★★★) #### 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 = \[\[1,2,3,4\], \[2,3,4,5\], \[3,4,5,6\], ..., \[11,12,13,14\]\]? (★★★) #### 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 (★★★) #### 82. Compute a matrix rank (★★★)
##### (hint: np.linalg.svd) (**hint**: np.linalg.svd)
#### 83. How to find the most frequent value in an array? #### 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 (★★★) #### 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\[j,i\] (★★★) #### 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)) (★★★) #### 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)? (★★★) #### 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 (★★★) #### 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) (★★★) #### 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? (★★★) #### 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 (★★★) #### 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? (★★★) #### 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 (★★★) #### 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? (★★★) #### 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 (★★★) #### 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 (★★★)? #### 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. (★★★) #### 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). (★★★) #### 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)