Added example
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Nicolas Rougier
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README.rst
95
README.rst
@ -46,7 +46,7 @@ Neophyte
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import numpy as np
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#. Print the numpy version and the configuration.
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2. Print the numpy version and the configuration.
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.. code:: python
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@ -54,52 +54,52 @@ Neophyte
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np.__config__.show()
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#. Create a null vector of size 10
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3. Create a null vector of size 10
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.. code:: python
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Z = np.zeros(10)
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#. Create a null vector of size 10 but the fifth value which is 1
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4. Create a null vector of size 10 but the fifth value which is 1
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.. code:: python
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Z = np.zeros(10)
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Z[4] = 1
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#. Create a vector with values ranging from 10 to 99
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5. Create a vector with values ranging from 10 to 99
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.. code:: python
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Z = np.arange(10,100)
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#. Create a 3x3 matrix with values ranging from 0 to 8
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6. Create a 3x3 matrix with values ranging from 0 to 8
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.. code:: python
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Z = np.arange(9).reshape(3,3)
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#. Find indices of non-zero elements from [1,2,0,0,4,0]
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7. Find indices of non-zero elements from [1,2,0,0,4,0]
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.. code:: python
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nz = np.nonzero([1,2,0,0,4,0])
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#. Declare a 3x3 identity matrix
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8. Declare a 3x3 identity matrix
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.. code:: python
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Z = np.eye(3)
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#. Declare a 5x5 matrix with values 1,2,3,4 just below the diagonal
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9. Declare a 5x5 matrix with values 1,2,3,4 just below the diagonal
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.. code:: python
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Z = np.diag(1+np.arange(4),k=-1)
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#. Declare a 10x10x10 array with random values
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10. Declare a 10x10x10 array with random values
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.. code:: python
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@ -108,7 +108,7 @@ Neophyte
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Novice
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======
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#. Declare a 8x8 matrix and fill it with a checkerboard pattern
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1. Declare a 8x8 matrix and fill it with a checkerboard pattern
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.. code:: python
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@ -116,20 +116,20 @@ Novice
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Z[1::2,::2] = 1
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Z[::2,1::2] = 1
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#. Declare a 10x10 array with random values and find the minimum and maximum values
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2. Declare a 10x10 array with random values and find the minimum and maximum values
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.. code:: python
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Z = np.random.random((10,10))
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Zmin, Zmax = Z.min(), Z.max()
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#. Create a checkerboard 8x8 matrix using the tile function
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3. Create a checkerboard 8x8 matrix using the tile function
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.. code:: python
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Z = np.tile( np.array([[0,1],[1,0]]), (4,4))
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#. Normalize a 5x5 random matrix (between 0 and 1)
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4. Normalize a 5x5 random matrix (between 0 and 1)
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.. code:: python
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@ -138,34 +138,34 @@ Novice
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Z = (Z - Zmin)/(Zmax - Zmin)
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#. Multiply a 5x3 matrix by a 3x2 matrix (real matrix product)
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5. Multiply a 5x3 matrix by a 3x2 matrix (real matrix product)
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.. code:: python
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Z = np.dot(np.ones((5,3)), np.ones((3,2)))
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#. Create a 10x10 matrix with row values ranging from 0 to 9
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6. Create a 10x10 matrix with row values ranging from 0 to 9
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.. code:: python
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Z = np.zeros((10,10))
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Z += np.arange(10)
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#. Create a vector of size 1000 with values ranging from 0 to 1, both excluded
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7. Create a vector of size 1000 with values ranging from 0 to 1, both excluded
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.. code:: python
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Z = np.random.linspace(0,1,1002,endpoint=True)[1:-1]
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#. Create a random vector of size 100 and sort it
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8. Create a random vector of size 100 and sort it
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.. code:: python
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Z = np.random.random(100)
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Z.sort()
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#. Consider two random matrices A anb B, check if they are equal.
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9. Consider two random matrices A anb B, check if they are equal.
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.. code:: python
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@ -173,7 +173,7 @@ Novice
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B = np.random.randint(0,2,(2,2))
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equal = np.allclose(A,B)
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#. Create a random vector of size 1000 and find the mean value
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10. Create a random vector of size 1000 and find the mean value
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.. code:: python
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@ -186,7 +186,7 @@ Apprentice
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==========
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#. Make an array immutable
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1. Make an array immutable
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.. code:: python
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@ -194,7 +194,7 @@ Apprentice
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Z.flags.writeable = False
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#. Consider a random 100x2 matrix representing cartesian coordinates, convert
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2. Consider a random 100x2 matrix representing cartesian coordinates, convert
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them to polar coordinates
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.. code:: python
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@ -205,7 +205,7 @@ Apprentice
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T = np.arctan2(Y,X)
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#. Create random vector of size 100 and replace the maximum value by 0
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3. Create random vector of size 100 and replace the maximum value by 0
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.. code:: python
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@ -213,7 +213,7 @@ Apprentice
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Z[Z.argmax()] = 0
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#. Declare a structured array with ``x`` and ``y`` coordinates covering the
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4. Declare a structured array with ``x`` and ``y`` coordinates covering the
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[0,1]x[0,1] area.
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.. code:: python
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@ -222,7 +222,7 @@ Apprentice
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Z['x'], Z['y'] = np.meshgrid(np.linspace(0,1,10),
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np.linspace(0,1,10))
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#. Print the minimum and maximum representable value for each numpy scalar type
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5. Print the minimum and maximum representable value for each numpy scalar type
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.. code:: python
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@ -235,7 +235,7 @@ Apprentice
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print np.finfo(dtype).eps
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#. Create a structured array representing a position (x,y) and a color (r,g,b)
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6. Create a structured array representing a position (x,y) and a color (r,g,b)
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.. code:: python
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@ -246,7 +246,7 @@ Apprentice
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('b', float, 1)])])
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#. Consider a random vector with shape (100,2) representing coordinates, find
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7. Consider a random vector with shape (100,2) representing coordinates, find
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point by point distances
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.. code:: python
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@ -261,7 +261,7 @@ Apprentice
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#. Generate a generic 2D Gaussian-like array
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8. Generate a generic 2D Gaussian-like array
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.. code:: python
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@ -270,7 +270,7 @@ Apprentice
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sigma, mu = 1.0, 0.0
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G = np.exp(-( (D-mu)**2 / ( 2.0 * sigma**2 ) ) )
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#. Consider the vector [1, 2, 3, 4, 5], how to build a new vector with 3
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9. Consider the vector [1, 2, 3, 4, 5], how to build a new vector with 3
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consecutive zeros interleaved between each value ?
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.. code:: python
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@ -283,7 +283,7 @@ Apprentice
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Z0[::nz+1] = Z
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#. Find the nearest value from a given value in an array
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10. Find the nearest value from a given value in an array
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.. code:: python
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@ -294,7 +294,7 @@ Apprentice
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Journeyman
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==========
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#. Consider the following file::
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1. Consider the following file::
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1,2,3,4,5
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6,,,7,8
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@ -307,7 +307,7 @@ Journeyman
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Z = genfromtxt("missing.dat", delimiter=",")
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#. Consider a generator function that generates 10 integers and use it to build an
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2. Consider a generator function that generates 10 integers and use it to build an
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array
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.. code:: python
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@ -318,7 +318,7 @@ Journeyman
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Z = np.fromiter(generate(),dtype=float,count=-1)
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#. Consider a given vector, how to add 1 to each element indexed by a second
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3. Consider a given vector, how to add 1 to each element indexed by a second
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vector (be careful with repeated indices) ?
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.. code:: python
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@ -330,7 +330,7 @@ Journeyman
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Z += np.bincount(I, minlength=len(Z))
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#. How to accumulate elements of a vector (X) to an array (F) based on an index
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4. How to accumulate elements of a vector (X) to an array (F) based on an index
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list (I) ?
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.. code:: python
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@ -341,7 +341,7 @@ Journeyman
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I = [1,3,9,3,4,1]
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F = np.bincount(I,X)
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#. Considering a (w,h,3) image of (dtype=ubyte), compute the number of unique
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5. Considering a (w,h,3) image of (dtype=ubyte), compute the number of unique
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colors
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.. code:: python
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@ -355,7 +355,7 @@ Journeyman
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np.unique(I)
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#. Considering a four dimensions array, how to get sum over the last two axis at once ?
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6. Considering a four dimensions array, how to get sum over the last two axis at once ?
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.. code:: python
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@ -365,10 +365,11 @@ Journeyman
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Craftsman
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=========
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#. Consider a one-dimensional array Z, build a two-dimensional array whose
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1. Consider a one-dimensional array Z, build a two-dimensional array whose
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first row is (Z[0],Z[1],Z[2]) and each subsequent row is shifted by 1 (last
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row should be (Z[-3],Z[-2],Z[-1])
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@ -383,7 +384,7 @@ Craftsman
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Z = rolling(np.arange(100), 3)
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#. Consider a set of 100 triplets describing 100 triangles (with shared
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2. Consider a set of 100 triplets describing 100 triangles (with shared
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vertices), find the set of unique line segments composing all the triangles.
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.. code:: python
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@ -399,11 +400,21 @@ Craftsman
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G = np.unique(G)
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3. Given an array C that is a bincount, how to procude an array A such that
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np.bincount(A) == C ?
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.. code:: python
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# Jaime Fernández del Río
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C = np.bincount([1,1,2,3,4,4,6])
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A = np.repeat(np.arange(len(C)), C)
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Artisan
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=======
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#. Considering a 100x3 matrix, extract rows with unequal values (e.g. [2,2,3])
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1. Considering a 100x3 matrix, extract rows with unequal values (e.g. [2,2,3])
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.. code:: python
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@ -413,7 +424,7 @@ Artisan
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E = np.logical_and.reduce(Z[:,1:] == Z[:,:-1], axis=1)
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U = Z[~E]
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#. Convert a vector of ints into a matrix binary representation.
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2. Convert a vector of ints into a matrix binary representation.
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.. code:: python
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@ -433,7 +444,7 @@ Artisan
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Adept
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=====
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#. Consider an arbitrary array, write a function that extract a subpart with a
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1. Consider an arbitrary array, write a function that extract a subpart with a
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fixed shape and centered on a given element (pad with a ``fill`` value when
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necessary)
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@ -473,7 +484,7 @@ Adept
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Expert
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======
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#. Consider two arrays A and B of shape (8,3) and (2,2). How to find rows of A
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1. Consider two arrays A and B of shape (8,3) and (2,2). How to find rows of A
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that contain elements of each row of B regardless of the order of the elements
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in B ?
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@ -488,7 +499,7 @@ Expert
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rows = (C.sum(axis=(1,2,3)) >= B.shape[1]).nonzero()[0]
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#. Extract all the contiguous 3x3 blocks from a random 10x10 matrix.
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2. Extract all the contiguous 3x3 blocks from a random 10x10 matrix.
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.. code:: python
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