`numpy.ma.core:diag`

Signature

def diag ( v , k = 0 )

Extract a diagonal or construct a diagonal array.

This function is the equivalent of numpy.diag that takes masked values into account, see numpy.diag for details.

import numpy as np

Create an array with negative values masked:

import numpy as np
x = np.array([[11.2, -3.973, 18], [0.801, -1.41, 12], [7, 33, -12]])
masked_x = np.ma.masked_array(x, mask=x < 0)
masked_x

Isolate the main diagonal from the masked array:

np.ma.diag(masked_x)

Isolate the first diagonal below the main diagonal:

np.ma.diag(masked_x, -1)