[SciPy-User] problems with numpy array assignment

[Gabriele Brambilla]

So if I do:

B2 = PAS1
Dx2 = ndimage.gaussian_filter(B2, sigma=[nsmopha, nsmoene])
B2 = Dx2

B1 = PAS1
Dx1 = ndimage.gaussian_filter(B1, sigma=[nsmopha, nsmoene])
B1 = Dx1

Am I applying the smooth two times?


2014-03-04 15:13 GMT-05:00 Gabriele Brambilla <
gb.gabrielebrambilla at gmail.com>:

> But the changes I make on  PAS=MYMAP[:, hhh. :] will be applied to
> G=MYMAP[:, :, :]?
>
> Gabriele
>
>
> 2014-03-04 15:07 GMT-05:00 Gabriele Brambilla <
> gb.gabrielebrambilla at gmail.com>:
>
> thanks.
>>
>> Gabriele
>>
>>
>> 2014-03-04 15:04 GMT-05:00 Eric Hermes <ehermes at chem.wisc.edu>:
>>
>>  On 3/4/2014 2:00 PM, Gabriele Brambilla wrote:
>>>
>>> Hi,
>>>
>>>  Something strange happens in my code: I have added the lines after #...
>>>
>>>  MYMAP is a 3d numpy array
>>> PAS = MYMAP[:, hhh, :]
>>>
>>>  #multiplying per energy bin width
>>>  PAS1 = PAS
>>> for l in nIph:
>>>          PAS1[l,:] = PAS1[l,:]*zz
>>>
>>>
>>>  But this affect the result I get when I elaborate the data from:
>>>
>>>  EXCT = MYMAP[:, hhh, :]
>>>
>>>  is python continuing to modify the original matrix??
>>>
>>>  Thanks
>>>
>>>  Gabriele
>>>
>>>
>>> _______________________________________________
>>> SciPy-User mailing listSciPy-User at scipy.orghttp://mail.scipy.org/mailman/listinfo/scipy-user
>>>
>>>  Gabriele,
>>>
>>> Numpy arrays are passed as references, so in your code when you modify
>>> PAS1 (which inherits the reference to MYMAP from PAS), the changes
>>> propogates upwards into MYMAP.  If you want to avoid this, you can
>>> explicitly create a copy of the array, either by doing:
>>>
>>> PAS = MYMAP[:,hhh,:].copy()
>>>
>>> or:
>>>
>>> PAS1 = PAS.copy()
>>>
>>> Eric
>>>
>>> --
>>> Eric Hermes
>>> J.R. Schmidt Group
>>> Chemistry Department
>>> University of Wisconsin - Madison
>>>
>>>
>>> _______________________________________________
>>> SciPy-User mailing list
>>> SciPy-User at scipy.org
>>> http://mail.scipy.org/mailman/listinfo/scipy-user
>>>
>>>
>>
>
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