[Numpy-discussion] how to multiply the rows of a matrix by a different number?
josef.pktd@gmai...
josef.pktd@gmai...
Tue Mar 3 20:11:09 CST 2009
On Tue, Mar 3, 2009 at 8:53 PM, Jose Borreguero <borreguero@gmail.com> wrote:
> I guess there has to be an easy way for this. I have:
> M.shape=(10000,3)
> N.shape=(10000,)
>
> I want to do this:
> for i in range(10000):
> M[i]*=N[i]
> without the explicit loop
>
>>> M = np.ones((10,3))
>>> N = np.arange(10)
>>> N.shape
(10,)
>>> (N[:,np.newaxis]).shape
(10, 1)
>>> M*N[:,np.newaxis]
array([[ 0., 0., 0.],
[ 1., 1., 1.],
[ 2., 2., 2.],
[ 3., 3., 3.],
[ 4., 4., 4.],
[ 5., 5., 5.],
[ 6., 6., 6.],
[ 7., 7., 7.],
[ 8., 8., 8.],
[ 9., 9., 9.]])
>>> M *= N[:,np.newaxis]
>>> M
Josef
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