[Numpy-discussion] NA.dot transposing in place

Curzio Basso curzio.basso at unibas.ch
Thu Jul 15 07:22:01 CDT 2004


Hi all.

I wonder if anyone noticed the following behaviour (new in 1.0) of the 
dot/matrixmultiply functions:

 >>> alpha = NA.arange(10, shape = (10,1))

 >>> beta = NA.arange(10, shape = (10,1))

 >>> NA.dot(alpha, alpha)
array([[285]])

 >>> alpha.shape # here it looks like it's doing the transpose in place
(1, 10)

 >>> NA.dot(beta, alpha)
array([[ 0,  0,  0,  0,  0,  0,  0,  0,  0,  0],
        [ 0,  1,  2,  3,  4,  5,  6,  7,  8,  9],
        [ 0,  2,  4,  6,  8, 10, 12, 14, 16, 18],
        [ 0,  3,  6,  9, 12, 15, 18, 21, 24, 27],
        [ 0,  4,  8, 12, 16, 20, 24, 28, 32, 36],
        [ 0,  5, 10, 15, 20, 25, 30, 35, 40, 45],
        [ 0,  6, 12, 18, 24, 30, 36, 42, 48, 54],
        [ 0,  7, 14, 21, 28, 35, 42, 49, 56, 63],
        [ 0,  8, 16, 24, 32, 40, 48, 56, 64, 72],
        [ 0,  9, 18, 27, 36, 45, 54, 63, 72, 81]])

 >>> alpha.shape, beta.shape # but not the second time
((1, 10), (10, 1))

-------------------------------------------------

Can someone explain me what's going on?

thanks, curzio




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