On Thu, 19 Aug 2010 09:06:32 -0500, G?khan Sever <[email protected]> wrote:
>On Thu, Aug 19, 2010 at 9:01 AM, greg whittier <[email protected]> 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) Be careful. This works for sums, but not for operations like median; the median of the row medians may not be the global median. So, you need to do the medians in one step. I'm not aware of a method cleaner than manually reshaping first. There may also be speed reasons to do things in one step. But, two steps may look cleaner in code. --jh-- _______________________________________________ NumPy-Discussion mailing list [email protected] http://mail.scipy.org/mailman/listinfo/numpy-discussion
