[Numpy-discussion] summing over more than one axis

Gökhan Sever gokhansever@gmail....
Thu Aug 19 09:06:32 CDT 2010


On Thu, Aug 19, 2010 at 9:01 AM, greg whittier <gregwh@gmail.com> wrote:

> I frequently deal with 3D data and would like to sum (or find the
> mean, etc.) over the last two axes.  I.e. sum a[i,j,k] over j and k.
> I find using .sum() really convenient for 2d arrays but end up
> reshaping 2d arrays to do this.  I know there has to be a more
> convenient way.  Here's what I'm doing
>
> a = np.arange(27).reshape(3,3,3)
>
> # sum over axis 1 and 2
> result = a.reshape((a.shape[0], a.shape[1]*a.shape[2])).sum(axis=1)
>
> Is there a cleaner way to do this?  I'm sure I'm missing something obvious.
>
> Thanks,
> Greg
>

Using two sums

np.sum(np.sum(a, axis=-2), axis=1)


-- 
Gökhan
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