[Numpy-discussion] Resize Method for Numpy Array

"V. Armando Solé" sole@esrf...
Thu Sep 24 10:38:14 CDT 2009


Alice Invernizzi wrote:
>  
> Dear all,
>
> I have an Hamletic doubt concerning the numpy array data type.
> A general learned rule concerning the array usage in other high-level
> programming languages is that array data-type are homogeneous datasets
> of  fixed dimension.
>
> Therefore, is not clear to me why in numpy the size of an array can be
> changed  (either with the 'returning-value' resize() function either with
> the 'in-place' array method resize()).
> More in detail, if the existence of the first function
> ('returning-value') might make sense in array computing operation, the
> existence of the 'in-place' method really make no sense for me.
>
> Would you please be so kind to give some explanation for the existence 
> of resize operator for numpy array? If array size can be change, 
> what are the real advantages of using numpy array instead of list object?
> Thanks in avdance 

Just to keep into the same line.

import numpy
a=numpy.arange(100.)
a.shape = 10, 10
b = a * 1 # just to get a copy
b.shape = 5, 2, 5, 5
b = (b.sum(axis=3)).sum(axis=1)

In that way, on b I have a binned image of a.

I would expect  a.resize(5, 5) would have given something similar 
(perhaps there is already something to make a binning). In fact 
a.resize(5,5) is much closer to a crop than to a resize. I think the 
resize name is misleading and should be called crop, but that is just my 
view.

Armando




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