Create random numpy matrix of same size as another.

Question

This question here was useful, but mine is slightly different.

I am trying to do something simple here, I have a numpy matrix A, and I simply want to create another numpy matrix B, of the same shape as A, but I want B to be created from numpy.random.randn() How can this be done? Thanks.

score 52 · Accepted Answer · edited Sep 27 '17 at 04:42

52

np.random.randn takes the shape of the array as its input which you can get directly from the shape property of the first array. You have to unpack a.shape with the * operator in order to get the proper input for np.random.randn.

a = np.zeros([2, 3])
print(a.shape)
# outputs: (2, 3)
b = np.random.randn(*a.shape)
print(b.shape)
# outputs: (2, 3)

edited Sep 27 '17 at 04:42

Graham

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answered Aug 09 '16 at 20:47

Chris Mueller

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Thanks! But what's with the '*'? – TheGrapeBeyond Aug 09 '16 at 20:50
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@TheGrapeBeyond It unpacks the arguments. Have a look at [this question](http://stackoverflow.com/questions/2921847/what-does-the-star-operator-mean-in-python). – Chris Mueller Aug 09 '16 at 20:51
Very interesting. Thanks, TIL. – TheGrapeBeyond Aug 09 '16 at 21:01

Create random numpy matrix of same size as another.

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