qr Builtin Function SSyynnooppssiiss QR decomposition SSyynnttaaxx qr ( _A ) qr ( _A, "p" ) DDeessccrriippttiioonn Qr computes the QR decomposition of the input matrix A such that: A = Q * R or A*p = Q * R Qr returns a list containing elements _q and _r. Optionally, qr can take a second argument, "p" which tells qr to perform column pivoting when computing _q and _r. The permutation matrix _p is returned in the same list as _q and _r. Qr utilizes LAPACK subroutines DGEQRF and DORGQR for REAL inputs, and ZGEQRF and ZUNGQR for COMPLEX inputs. When column pivoting is requested the LAPACK subroutines DGEQPF, and ZGEQPF are used.