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EigValVecSymTri

Compute the eigenvalues and eigenvectors of a real symmetric tridiagonal matrix.

Usage

eval, evec = pyshtools.EigValVecSymTri (ain, [n, ul])

Returns

eval : float, dimension (n)
The eigenvalues of ain, sorted from largest to smallest.
evec : float, dimension (n, n)
The eigenvectors of ain, sorted from largest to smallest eigenvalues. The sign of the first element of each eigenvector is chosen to be positive.

Parameters

ain : float, dimension (nin, nin)
The input real symmetric tridiagonal matrix.
n : optional, integer, default = nin
The rank of the matrix ain.
ul : optional, character, default = L
If U then the upper portion of the matrix ain will be used. If L then the lower portion of the matrix ain will be used (default).

Description

EigValVecSymTri will calculate the eigenvalues and eigenvectors of a real symmetric tridiagonal matrix. By default, only the lower portion of the matrix is used, but this can be changed by the optional argument ul. The eigenvalues and eigenvectors are sorted from largest to smallest eigenvalues, and the sign of the first element of each eigenvector is chosen to be positive. This routine factors the matrix ain using the LAPACK routine DSTEGR.

See also

eigvalsym, eigvalvecsym

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