I have to np arrays
a = np.array[[1,2]
[2,3]
[3,4]
[5,6]]
b = np.array [[2,4]
[6,8]
[10,11]
I want to multiple each row of a against each element in array b so that array c is created with dimensions of a-rows xb rows (as columns)
c = np.array[[2,8],[6,16],[10,22]
[4,12],[12,21],[20,33]
....]
There are other options for doing this, but I would really like to leverage the speed of numpy's ufuncs...if possible.
any and all help is appreciated.
Does this do what you want?
>>> a
array([[1, 2],
[2, 3],
[3, 4],
[5, 6]])
>>> b
array([[ 2, 4],
[ 6, 8],
[10, 11]])
>>> a[:,None,:]*b
array([[[ 2, 8],
[ 6, 16],
[10, 22]],
[[ 4, 12],
[12, 24],
[20, 33]],
[[ 6, 16],
[18, 32],
[30, 44]],
[[10, 24],
[30, 48],
[50, 66]]])
>>> _.shape
(4, 3, 2)
Or if that doesn't have the right shape, you can reshape it:
>>> (a[:,None,:]*b).reshape((a.shape[0]*b.shape[0], 2))
array([[ 2, 8],
[ 6, 16],
[10, 22],
[ 4, 12],
[12, 24],
[20, 33],
[ 6, 16],
[18, 32],
[30, 44],
[10, 24],
[30, 48],
[50, 66]])
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