pyyeti.ytools.isdiag

pyyeti.ytools.isdiag(A, tol=1e-12)[source]

Checks contents of square matrix A to see if it is approximately diagonal.

Parameters:

  • A (2d numpy array) – If not square or if number of dimensions does not equal 2, this routine returns False.

  • tol (scalar; optional) – The tolerance value.

Returns:

True if A is a diagonal matrix, False otherwise.

Notes

If all off-diagonal values are less than tol times the maximum diagonal value (absolute-valuewise), this routine returns True. Otherwise, False is returned.

See also

mattype()

Examples

>>> from pyyeti import ytools
>>> import numpy as np
>>> A = np.diag(np.arange(5.0))
>>> ytools.isdiag(A)
True
>>> A[0, 2] = .01
>>> A[2, 0] = .01
>>> ytools.isdiag(A)  # symmetric but not diagonal
False
>>> ytools.isdiag(A[1:, :])  # non-square
False