[Numpy-discussion] kind of a matrix multiplication

Martin Raspaud martin.raspaud@smhi...
Tue Oct 11 00:49:10 CDT 2011


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Hi all,

I have a stack of vectors:

v1 = np.arange(3)
v2 = np.arange(3) + 3
stack = np.vstack(v1, v2)

(now stack is :
array([[0, 1, 2],
       [3, 4, 5]]))

and a 3d matrix:

mat = np.dstack((np.eye(3), np.eye(3) * 2))
(mat is now
array([[[ 1.,  2.],
        [ 0.,  0.],
        [ 0.,  0.]],

       [[ 0.,  0.],
        [ 1.,  2.],
        [ 0.,  0.]],

       [[ 0.,  0.],
        [ 0.,  0.],
        [ 1.,  2.]]]))

I'm looking for the operation needed to get the two (stacked) vectors
array([[0, 1, 2],
       [6, 8, 10]]))
or its transpose.

I tried various combinations of tensor products, but I always get a
result in 3 dimensions, while I just want two.

Any suggestions ?

Thanks,
Martin
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