# dorg2r.f - Man Page

SRC/dorg2r.f

## Synopsis

### Functions/Subroutines

subroutine **dorg2r** (m, n, k, a, lda, tau, work, info)**DORG2R** generates all or part of the orthogonal matrix Q from a QR factorization determined by sgeqrf (unblocked algorithm).

## Function/Subroutine Documentation

### subroutine dorg2r (integer m, integer n, integer k, double precision, dimension( lda, * ) a, integer lda, double precision, dimension( * ) tau, double precision, dimension( * ) work, integer info)

**DORG2R** generates all or part of the orthogonal matrix Q from a QR factorization determined by sgeqrf (unblocked algorithm).

**Purpose:**

DORG2R generates an m by n real matrix Q with orthonormal columns, which is defined as the first n columns of a product of k elementary reflectors of order m Q = H(1) H(2) . . . H(k) as returned by DGEQRF.

**Parameters***M*M is INTEGER The number of rows of the matrix Q. M >= 0.

*N*N is INTEGER The number of columns of the matrix Q. M >= N >= 0.

*K*K is INTEGER The number of elementary reflectors whose product defines the matrix Q. N >= K >= 0.

*A*A is DOUBLE PRECISION array, dimension (LDA,N) On entry, the i-th column must contain the vector which defines the elementary reflector H(i), for i = 1,2,...,k, as returned by DGEQRF in the first k columns of its array argument A. On exit, the m-by-n matrix Q.

*LDA*LDA is INTEGER The first dimension of the array A. LDA >= max(1,M).

*TAU*TAU is DOUBLE PRECISION array, dimension (K) TAU(i) must contain the scalar factor of the elementary reflector H(i), as returned by DGEQRF.

*WORK*WORK is DOUBLE PRECISION array, dimension (N)

*INFO*INFO is INTEGER = 0: successful exit < 0: if INFO = -i, the i-th argument has an illegal value

**Author**Univ. of Tennessee

Univ. of California Berkeley

Univ. of Colorado Denver

NAG Ltd.

Definition at line **113** of file **dorg2r.f**.

## Author

Generated automatically by Doxygen for LAPACK from the source code.

## Referenced By

The man page dorg2r(3) is an alias of dorg2r.f(3).

Tue Nov 28 2023 12:08:42 Version 3.12.0 LAPACK