[Numpy-discussion] dot() function question

Warren Weckesser warren.weckesser@enthought....
Wed Jun 27 17:01:38 CDT 2012


On Wed, Jun 27, 2012 at 4:38 PM, <x.piter@gmail.com> wrote:

> Hi list.
> I have got completely cunfused with the numpy.dot() function.
> dot(A,B) does:
> - matrix multiplication if A and B are of MxN and NxK sizey
> - dot product if A and B are of size M
> How how can I perform matrix multiplication of two vectors?
> (in matlab I do it like a*a')
>


If 'a' is a 1D numpy array, you can use numpy.outer:


In [6]: a = array([1, -2, 3])

In [7]: outer(a, a)
Out[7]:
array([[ 1, -2,  3],
       [-2,  4, -6],
       [ 3, -6,  9]])


Warren



> Thanks.
> Petro.
>
>
>
>
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