naginterfaces.library.lapackeig.ztrexc

naginterfaces.library.lapackeig.ztrexc(compq, t, q, ifst, ilst)[source]

ztrexc reorders the Schur factorization of a complex general matrix.

For full information please refer to the NAG Library document for f08qt

https://support.nag.com/numeric/nl/nagdoc_30.2/flhtml/f08/f08qtf.html

Parameters
compqstr, length 1

Indicates whether the matrix of Schur vectors is to be updated.

The matrix of Schur vectors is updated.

No Schur vectors are updated.

tcomplex, array-like, shape

The upper triangular matrix , as returned by zhseqr().

qcomplex, array-like, shape

Note: the required extent for this argument in dimension 1 is determined as follows: if : ; if : ; otherwise: .

Note: the required extent for this argument in dimension 2 is determined as follows: if : ; if : ; otherwise: .

If , must contain the unitary matrix of Schur vectors.

ifstint

and must specify the reordering of the diagonal elements of . The element with row index is moved to row by a sequence of exchanges between adjacent elements.

ilstint

and must specify the reordering of the diagonal elements of . The element with row index is moved to row by a sequence of exchanges between adjacent elements.

Returns
tcomplex, ndarray, shape

is overwritten by the updated matrix .

qcomplex, ndarray, shape

If , contains the updated matrix of Schur vectors.

If , is not referenced.

Raises
NagValueError
(errno )

On entry, error in parameter .

Constraint: or .

(errno )

On entry, error in parameter .

Constraint: .

(errno )

On entry, error in parameter .

Constraint: .

(errno )

On entry, error in parameter .

Constraint: .

Notes

ztrexc reorders the Schur factorization of a complex general matrix , so that the diagonal element of with row index is moved to row .

The reordered Schur form is computed by a unitary similarity transformation: . Optionally the updated matrix of Schur vectors is computed as , giving .

References

Golub, G H and Van Loan, C F, 1996, Matrix Computations, (3rd Edition), Johns Hopkins University Press, Baltimore