ValueError: 'axis' entry is out of bounds // numpy

问题:

Here is my 2D numpy array:

returns = np.array([  [ -4.78878057e-03   9.79090927e-03  -2.06883581e-03  -1.25786164e-02]  [  5.79128440e-03  -2.85791008e-03   1.69555388e-03  -5.63798220e-02]  [  5.73427375e-05   2.45043133e-02   8.55025651e-03  -4.53257790e-02]  [  6.75441635e-03   8.70168484e-03   1.07547532e-02  -1.36919315e-01]  [  6.68332655e-03   6.76498174e-03   3.08225775e-03   0.00000000e+00]]) 

And when I'm trying to calculate the STD for each column:

print np.std(returns, axis=1) 

I'm getting the following error:

ValueError: 'axis' entry is out of bounds 

How can I fix that?

回答1:

Check if your array is a 2-D array querying a.ndim. It may happen that you have a 1-D array of objects that, when printed, looks like a 2-D array. In this case you can convert it to a 2-D array doing:

a = np.array(list(a)) 

or

a = np.array(tuple(a)) 

回答2:

Michael,

I am not sure why you have the issue. It might be because of the way you are defining the 2D array (that's my only guess). I used the following code and it works properly:

import numpy as np  arr = np.array([                                                                \ [ -4.78878057e-03,   9.79090927e-03,  -2.06883581e-03,  -1.25786164e-02],       \ [  5.79128440e-03,  -2.85791008e-03,   1.69555388e-03,  -5.63798220e-02],       \ [  5.73427375e-05,   2.45043133e-02,   8.55025651e-03,  -4.53257790e-02],       \ [  6.75441635e-03,   8.70168484e-03,   1.07547532e-02,  -1.36919315e-01],       \ [  6.68332655e-03,   6.76498174e-03,   3.08225775e-03,   0.00000000e+00]        \ ])  std = np.std(arr,axis=1) print std 

and the answer will be:

[ 0.00803178  0.02526721  0.02593599  0.06308687  0.00281146] 

回答3:

Recently had this same problem:

np.sum(myndarray, axis=0) 

was producing the "ValueError: 'axis' entry is out of bounds" error when executed inside a function called from a script. Strangely, when executing the line from the IPython shell it ran without a hitch (I checked that the myndarray variable was the same in both contexts).

I was working with Spyder, so perhaps it somehow got stuck in a weird state as a result of using the Python console + pdb, and/or IPython + ipdb, with the same set of variables. Restarting the IDE solved the issue, which also explains the others' inability to reproduce the bug.

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