matrices multiplication using numpy

Question

In the following code, why is there an output, mathematically it should give an error

import numpy as np                                                                                                                                                      
arr = np.array([[1., 2., 3.], [4., 5., 6.]])                                                                                                                                                                                                                                                                                               

out:
array([[1., 2., 3.],
       [4., 5., 6.]])

arr*arr                                                                                                                                                                  

out : array([[ 1.,  4.,  9.],
            [16., 25., 36.]])

That's element-wise multiplication when operating on arrays. The operator for matrix multiplication is @ — user3483203
– user3483203, Commented Jun 22, 2021 at 14:20

Jonathan Schwartz · Accepted Answer · 2021-06-22 14:29:18Z

2

The * operator multiplies values in place. It seems like you want the @ operator, which performs a dot product between the two matrices.

Example:

a = np.array([[1, 2])
b = np.array([[3], [5]])

a * b returns: [[3, 6],[5, 10]]

a @ b returns: 13

answered Jun 22, 2021 at 14:29

Jonathan Schwartz

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