[Numpy-discussion] combinatorial operations on a pair of arrays

Damien Moore damienlmoore@gmail....
Wed Nov 18 14:43:09 CST 2009


ugh... I goofed. The code snippet should have read

from numpy import *
A=array([[1,2],[2,3],[3,4]])
B=array([[2,2],[3,3]])
C=zeros(A.shape)
for i in xrange(len(A)):
 C[i]=(A[i]**B).sum(0)
print C


On Wed, Nov 18, 2009 at 2:17 PM, Damien Moore <damienlmoore@gmail.com> wrote:
> The title of this e-mail is probably misleading so let me just show some code:
>
> from numpy import *
> A=array([[1,2],[2,3],[3,4]])
> B=array([[2,2],[3,3]])
> C=zeros(A.shape)
> for i in xrange(len(A)):
>  C[i]=sum(A[i]**B)
> print C
>
> What I want to do is eliminate the for loop and rely on numpy
> internals, but I'm not sure how to do this most efficiently.
>
> The fundamental aspect of the operation is that the array C is
> constructed by applying each subarray B to each subarray of A (i.e.
> all permutations) and then summing over a subset.
>


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