# naginterfaces.library.lapackeig.dormqr¶

naginterfaces.library.lapackeig.dormqr(side, trans, a, tau, c)[source]

dormqr multiplies an arbitrary real matrix by the real orthogonal matrix from a factorization computed by dgeqrf() or dgeqp3().

For full information please refer to the NAG Library document for f08ag

https://www.nag.com/numeric/nl/nagdoc_29/flhtml/f08/f08agf.html

Parameters
sidestr, length 1

Indicates how or is to be applied to .

or is applied to from the left.

or is applied to from the right.

transstr, length 1

Indicates whether or is to be applied to .

is applied to .

is applied to .

afloat, array-like, shape

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

Details of the vectors which define the elementary reflectors, as returned by dgeqrf() or dgeqp3().

taufloat, array-like, shape

Further details of the elementary reflectors, as returned by dgeqrf() or dgeqp3().

cfloat, array-like, shape

The matrix .

Returns
cfloat, ndarray, shape

is overwritten by or or or as specified by and .

Raises
NagValueError
(errno )

On entry, error in parameter .

Constraint: or .

(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: .

(errno )

On entry, error in parameter .

Constraint: .

Notes

dormqr is intended to be used after a call to dgeqrf() or dgeqp3() which perform a factorization of a real matrix . The orthogonal matrix is represented as a product of elementary reflectors.

This function may be used to form one of the matrix products

overwriting the result on (which may be any real rectangular matrix).

A common application of this function is in solving linear least squares problems, as described in the F08 Introduction.

References

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