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From: Ian Kelly <ian.g.kelly@gmail.com>
Date: Thu, 20 Sep 2012 13:29:23 -0600
Subject: Re: looping in array vs looping in a dic
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On Thu, Sep 20, 2012 at 1:28 PM, Ian Kelly <ian.g.kelly@gmail.com> wrote:
> Expanding on what MRAB wrote, since you probably have far fewer
> categories than pixels, you may be able to take better advantage of
> numpy's vectorized operations (which are pretty much the whole point
> of using numpy in the first place) by looping over the categories
> instead:
>
> for cat in categories:
>     totals[cat] += np.sum(valuesCategory * (valuesRaster == cat))

Of course, that should have read:

for cat in categories:
    totals[cat] += np.sum(valuesRaster * (valuesCategory == cat))