[Numpy-discussion] sum returns grand total?
Travis Oliphant
oliphant at ee.byu.edu
Mon Sep 11 10:47:18 CDT 2006
listservs at mac.com wrote:
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>I must have missed something -- since when does summing a
>multidimensional array return the grand total? I thought that it
>should sum over axis zero by default (at least, thats what the docs
>say). Here's what I am getting:
>
>(Pdb) pre
>Out[6]:
>array([[[ 13, 3, 1, 33, 52],
> [ 1, 0, 0, 0, 2],
> [ 4, 0, 0, 2, 6],
> [ 15, 1, 0, 20, 54]],
>
> [[380, 101, 9, 267, 321],
> [ 20, 4, 0, 7, 16],
> [ 31, 3, 1, 31, 22],
> [314, 27, 4, 276, 391]]], dtype=int64)
>(Pdb) sum(pre)
>Out[6]: 2432L
>
>Is this correct behaviour?
>
>
Yes, you need to specify which axis you want to sum over if you have a
multi-dimensional array. This is the "basic" behavior of most functions
in numpy unless you import them from oldnumeric. See the
fix_default_axis.py file for help on converting code that worked for
numpy 0.9.8 to 1.0 where this switch was made.
-Travis
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