On Thu, Jul 19, 2012 at 5:52 AM, Cheng Li
Hi All,****
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I have spot a strange behavior of numpy.fromfunction(). The sample codes are as follows:****
import numpy as np****
def myOnes(i,j):****
return 1.0****
a = np.fromfunction(myOnes,(2000,2000))****
a****
1.0****
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Actually what I expected is that the function will return a 2000*2000 2d array with unit value. The returned single float value really confused me. Is this a known bug? The numpy version I used is 1.6.1.****
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Your function will be called *once*, with arguments that are *arrays* of coordinate values. It must handle these arrays when it computes the values of the array to be created. To see what is happening, print the values of i and j from within your function, e.g.: In [57]: def ijsum(i, j): ....: print "i =", i ....: print "j =", j ....: return i + j ....: In [58]: fromfunction(ijsum, (3, 4)) i = [[ 0. 0. 0. 0.] [ 1. 1. 1. 1.] [ 2. 2. 2. 2.]] j = [[ 0. 1. 2. 3.] [ 0. 1. 2. 3.] [ 0. 1. 2. 3.]] Out[58]: array([[ 0., 1., 2., 3.], [ 1., 2., 3., 4.], [ 2., 3., 4., 5.]]) Your `myOnes` function will work if you modify it something like this: In [59]: def myOnes(i, j): ....: return np.ones(i.shape) ....: In [60]: fromfunction(myOnes, (3, 4)) Out[60]: array([[ 1., 1., 1., 1.], [ 1., 1., 1., 1.], [ 1., 1., 1., 1.]]) The bug is in the docstring for fromfunction. In the description of the `function` argument, it says "`function` must be capable of operating on arrays, and should return a scalar value." But the function should *not* return a scalar value. It should return an array of values appropriate for the given arguments. Warren
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Regards,****
Cheng****
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