# mxnet.np.linalg.eigvals¶

eigvals(a)

Compute the eigenvalues of a general matrix.

Main difference between eigvals and eig: the eigenvectors aren’t returned.

Parameters

a ((.., M, M) ndarray) – A real-valued matrix whose eigenvalues will be computed.

Returns

w – The eigenvalues, each repeated according to its multiplicity. They are not necessarily ordered.

Return type

(.., M,) ndarray

Raises

MXNetError – If the eigenvalue computation does not converge.

eig()

eigenvalues and right eigenvectors of general arrays

eigh()

eigenvalues and eigenvectors of a real symmetric array.

eigvalsh()

eigenvalues of a real symmetric.

()

Broadcasting rules apply, see the numpy.linalg documentation for details. This is implemented using the _geev LAPACK routines which compute the eigenvalues and eigenvectors of general square arrays. This function differs from the original numpy.linalg.eigvals in the following way(s): * Does not support complex input and output.

Examples

Illustration, using the fact that the eigenvalues of a diagonal matrix are its diagonal elements, that multiplying a matrix on the left by an orthogonal matrix, Q, and on the right by Q.T (the transpose of Q), preserves the eigenvalues of the “middle” matrix. In other words, if Q is orthogonal, then Q * A * Q.T has the same eigenvalues as A:

>>> from numpy import linalg as LA
>>> x = np.random.random()
>>> Q = np.array([[np.cos(x), -np.sin(x)], [np.sin(x), np.cos(x)]])
>>> LA.norm(Q[0, :]), LA.norm(Q[1, :]), np.dot(Q[0, :],Q[1, :])
(1.0, 1.0, 0.0)


Now multiply a diagonal matrix by Q on one side and by Q.T on the other:

>>> D = np.diag((-1,1))
>>> LA.eigvals(D)
array([-1.,  1.])
>>> A = np.dot(Q, D)
>>> A = np.dot(A, Q.T)
>>> LA.eigvals(A)
array([ 1., -1.]) # random