# naginterfaces.library.lapackeig.dorgtr¶

naginterfaces.library.lapackeig.dorgtr(uplo, a, tau)[source]

dorgtr generates the real orthogonal matrix , which was determined by dsytrd() when reducing a symmetric matrix to tridiagonal form.

For full information please refer to the NAG Library document for f08ff

https://www.nag.com/numeric/nl/nagdoc_28.6/flhtml/f08/f08fff.html

Parameters
uplostr, length 1

This must be the same argument as supplied to dsytrd().

afloat, array-like, shape

Details of the vectors which define the elementary reflectors, as returned by dsytrd().

taufloat, array-like, shape

Further details of the elementary reflectors, as returned by dsytrd().

Returns
afloat, ndarray, shape

The orthogonal matrix .

Raises
NagValueError
(errno )

On entry, error in parameter .

Constraint: or .

(errno )

On entry, error in parameter .

Constraint: .

Notes

dorgtr is intended to be used after a call to dsytrd(), which reduces a real symmetric matrix to symmetric tridiagonal form by an orthogonal similarity transformation: . dsytrd() represents the orthogonal matrix as a product of elementary reflectors.

This function may be used to generate explicitly as a square matrix.

References

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