[Numpy-discussion] how to assign to a "sub set" of an array

Timothy Hochberg tim.hochberg@ieee....
Wed Nov 14 10:59:00 CST 2007


On Nov 14, 2007 9:08 AM, Sebastian Haase <haase@msg.ucsf.edu> wrote:

> Hi,
> First here is some test I ran, where I think the last command shows a bug:
>
> >>> a = N.arange(4); a.shape=2,2; a
> [[0 1]
>  [2 3]]
> >>> aa = N.array((a,a,a)); aa
> [[[0 1]
>  [2 3]]
>
>  [[0 1]
>  [2 3]]
>
>  [[0 1]
>  [2 3]]]
> >>> N.nonzero(a==0)
> ([0], [0])
> >>> aa[N.nonzero(a==0)] = 5,5; aa
> [[[        5 544434034]
>  [        2         3]]
>
>  [[        0         1]
>  [        2         3]]
>
>  [[        0         1]
>  [        2         3]]]
>
>
> What happend here ?  The value 544434034 is different every time.....


I'm not seeing that here on WinXP with numpy 1.0.4.dev3462 ; can you tell me
what platform and version you are using?





>
> Background:
> I have a gray-scale 2D image (in this examples it's a 2x2 pixel image
> named 'a')
> I would like to show this image using grey-values EXCEPT I would like
> to show 0-values as blue.
> For use with pyOpenGL textures, I convert the image into an RGB image,
> in the example called 'aa', with shape 3,2,2.
>
> This is where I'm getting lost, and I tried assigning "something"
> (5,5) to aa "only at certain pixels"....
> Maybe someone can teach what the proper indexing-constuct, that I
> would need to do what I want.
>
> Did I find a bug ?


It looks like a bug, although it's possible it's been fixed. Or maybe it's a
new one and I need to update my version of numpy to see it...


>
>
> Thanks,
> Sebastian Haase
> _______________________________________________
> Numpy-discussion mailing list
> Numpy-discussion@scipy.org
> http://projects.scipy.org/mailman/listinfo/numpy-discussion
>



-- 
.  __
.   |-\
.
.  tim.hochberg@ieee.org
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