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Diagonal matrices

We often want to make matrices with all zeros except on the diagonal – diagonal matrices.

Numpy does not fail us:

>>> import numpy as np
>>> np.diag([3, 4, 5, 6])
array([[3, 0, 0, 0],
       [0, 4, 0, 0],
       [0, 0, 5, 0],
       [0, 0, 0, 6]])

>>> np.diag([7, 8, 9, 10, 11])
array([[ 7,  0,  0,  0,  0],
       [ 0,  8,  0,  0,  0],
       [ 0,  0,  9,  0,  0],
       [ 0,  0,  0, 10,  0],
       [ 0,  0,  0,  0, 11]])