[Numpy-discussion] vectorizing histogram-like computation

Perry Greenfield perry at stsci.edu
Mon Jun 20 12:32:15 CDT 2005


On Jun 20, 2005, at 3:09 PM, Piotr Luszczek wrote:

> All,
>
> I apologize if this is a dupe. I haven't seen it where I looked.
>
> There is numarray.numeric.histogram and numarray.mlab.histogram.
> What they do is this (more or less):
>
> for idx in arr:
>    histogram[idx] += 1
>
> What I want to do is:
>
> for idx in arr:
>    result[idx] ^= value
>
> Doing:
>
> result[arr] ^= value
>
> doesn't work. Which is not surprising because:
>
> histogram[arr] += 1
>
> doesn't work either.
>
> My question is whether there is a way to do it (the XOR example)
> without using a for loop.
>
> Thanks,
>
> Piotr

Not that I'm aware of. It suggests that there may be a need to expand 
on the histogram-like functionality to handle this sort of thing, 
though I wonder how often it would be used.

Perry Greenfield





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