[SciPy-user] matrix multipy ...
Johann Cohen-Tanugi
cohen@slac.stanford....
Mon May 19 13:44:53 CDT 2008
hi Matteo,
In [1]: import numpy as np
In [2]: aa = np.mat("1,2,3,4,5;6,7,8,9,0")
In [3]: bb = np.mat("1,2,3;4,5,6")
In [4]: np.outer(aa.T,bb)
Out[4]:
array([[ 1, 2, 3, 4, 5, 6],
[ 6, 12, 18, 24, 30, 36],
[ 2, 4, 6, 8, 10, 12],
[ 7, 14, 21, 28, 35, 42],
[ 3, 6, 9, 12, 15, 18],
[ 8, 16, 24, 32, 40, 48],
[ 4, 8, 12, 16, 20, 24],
[ 9, 18, 27, 36, 45, 54],
[ 5, 10, 15, 20, 25, 30],
[ 0, 0, 0, 0, 0, 0]])
In [5]: np.outer(aa,bb)
Out[5]:
array([[ 1, 2, 3, 4, 5, 6],
[ 2, 4, 6, 8, 10, 12],
[ 3, 6, 9, 12, 15, 18],
[ 4, 8, 12, 16, 20, 24],
[ 5, 10, 15, 20, 25, 30],
[ 6, 12, 18, 24, 30, 36],
[ 7, 14, 21, 28, 35, 42],
[ 8, 16, 24, 32, 40, 48],
[ 9, 18, 27, 36, 45, 54],
[ 0, 0, 0, 0, 0, 0]])
Is that what you were looking for?
cheers,
Johann
Matteo Bertini wrote:
> Perhaps it's simple, but...
>
> Suppose I have 2 "vectors" (1xN matrix really)
>
> n [27]: a = mat("1,2,3,4,5")
> In [29]: b = mat("1,2,3")
>
> If I whant the product, no problem.
>
> But suppose I have a list of vectors (a proper matrix)
>
> In [37]: aa = mat("1,2,3,4,5;6,7,8,9,0")
> In [38]: bb = mat("1,2,3;4,5,6")
>
> Can I avoid a loop and have the resulting "cube"?
>
> In [40]: aa[0].T*bb[0]
> Out[40]:
> matrix([[ 1, 2, 3],
> [ 2, 4, 6],
> [ 3, 6, 9],
> [ 4, 8, 12],
> [ 5, 10, 15]])
>
> I admit, I can't really understand array slicing power/limits!
>
> Thank you,
> Matteo Bertini
>
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