[Q,R] = QR(X) produces an upper triangular matrix R of
the same dimension as X and a unitary matrix Q so that
X = Q*R.
[Q,R,E] = QR(X) produces a permutation matrix E , an
upper triangular R with decreasing diagonal elements and
a unitary Q so that X*E = Q*R.
By itself, QR(X) returns the output of LINPACK'S ZQRDC
routine. TRIU (QR(X)) is R.
See also QRDELETE , QRINSERT .