[Numpy-discussion] array vector elementwise multiplication
Charles R Harris
charlesr.harris@gmail....
Tue Feb 3 19:09:52 CST 2009
On Tue, Feb 3, 2009 at 10:19 AM, Gideon Simpson <simpson@math.toronto.edu>wrote:
> I have an M x N matrix A and two vectors, an M dimensional vector x
> and an N dimensional vector y. I would like to be able to do two
> things.
>
> 1. Multiply, elementwise, every column of A by x
>
> 2. Multiply, elementwise, every row of A by y.
>
> What's the "quick" way to do this in numpy?
>
In [1]: M = ones((3,3))
In [2]: x = arange(3)
In [3]: M*x
Out[3]:
array([[ 0., 1., 2.],
[ 0., 1., 2.],
[ 0., 1., 2.]])
In [4]: x[:,newaxis]*M
Out[4]:
array([[ 0., 0., 0.],
[ 1., 1., 1.],
[ 2., 2., 2.]])
Chuck
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