Matrix creation
import numpy as np
x = np.array([[1,2],[3,4]])
y = np.array([[5,6],[7,8]])Element wise multiplication
>>> x * y
array([[ 5, 12],
[21, 32]])Matrix multiplication
>>> x @ y
array([[19, 22],
[43, 50]])Tensor product
>>> np.kron(x,y)
array([[ 5, 6, 10, 12],
[ 7, 8, 14, 16],
[15, 18, 20, 24],
[21, 24, 28, 32]])
Trace
>>> np.einsum('ii',x)
5norm
(i.e. summing all values of the matrix)
>>> np.einsum('ij->',x)
10Sum over rows/columns
>>> np.einsum('ij->i',x)
array([3, 7])
>>> np.einsum('ij->j',x)
array([4, 6])