[Numpy-discussion] Multiply along axis

Robert Elsner mlist@re-factory...
Wed Jun 29 09:35:59 CDT 2011


Oh and I forgot to mention: I want to specify the axis so that it is
possible to multiply x along an arbitrary axis of a (given that the
lengths match).

On 29.06.2011 16:32, Robert Elsner wrote:
> Hello everyone,
>
> I would like to solve the following problem (preferably without
> reshaping / flipping the array a).
>
> Assume I have a vector v of length x and an n-dimensional array a where
> one dimension has length x as well. Now I would like to multiply the
> vector v along a given axis of a.
>
> Some example code
>
> a = np.random.random((2,3))
> x = np.zeros(2)
>
> a * x	# Fails because not broadcastable
>
>
> So how do I multiply x with the columns of a so that for each column j
> a[:,j] = a[:,j] * x
>
> without using a loop. Is there some (fast) fast way to accomplish that
> with numpy/scipy?
>
> Thanks for your help
> Robert Elsner
>
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