how to multiply two matrices with different size?

[Ian Kelly]

On Fri, Nov 18, 2016 at 6:51 PM,  <limetree377 at gmail.com> wrote:
> Hi :)
> I'm trying to multiply two matrices that has different size.
>
> -------------------------------------code-------------------------
>
> import numpy as np
>
> a = np.random.randn(4, 3)
> b = np.random.randn(4, 1)
>
> print a
> print b
>
> -------------------------------------code-------------------------
>
> How should I multiply a and b so that the multipled matrix's size is 4*3?
>
> I want to multiply matrix 'b' to each row of matrix 'a'.
> So that if matrix a is
> [[1, 2, 3],
>   [2, 3, 4]]
> and b is
> [[2],
> [3]]
> a*b is
> [[2, 4, 6],
>   [4, 6 ,8]]
>
> Plz help me!
>
> if possible, plz use numpy

You don't need to do anything special.

>>> import numpy as np
>>> a = np.array([[1,2,3],[2,3,4]])
>>> b = np.array([[2], [3]])
>>> a
array([[1, 2, 3],
       [2, 3, 4]])
>>> b
array([[2],
       [3]])
>>> a * b
array([[ 2,  4,  6],
       [ 6,  9, 12]])

(I'm assuming this is actually the output you want. The output you
posted is jut a * 2.)