qr.Matrix(x, pivot=F, tune=<see below>, workspace=<see below>)
x
, indicating
whether or not each column is free for pivoting. The parameter
pivot
can
also be a single logical value, indicating either that all or no columns
are free for pivoting. By default, no column pivoting is done.
NB
,
NBMIN
, and
NX
as described in
.laenv
.
This parameter has no effect when pivoting is allowed.
The default is to use the settings in
.laenv
, which in S-PLUS is initialized
to use an unblocked algorithm (
NB = 1
), but may be changed by the user.
tune
.
The optimal workspace for the problem (for the given
tune
specifications) is
included as part of the output attributes.
x
is returned as
an object of class
c("qr.Matrix", "decomp")
.
A copy of the call to
qr.Matrix
is included as an attribute.
Based on the functions dgeqrf, dgeqpf, zgeqrf, and zgeqpf from LAPACK
(Anderson et al. 1994).
Parameters in
tune
may affect performance and workspace requirements,
but the optimal settings are both machine and problem dependent.
Users may want to experiment with
tune
(see Anderson et al., p. 72-74)
to obtain improved performance.
Anderson, E., et al. (1994). LAPACK User's Guide, 2nd edition, SIAM, Philadelphia.
A <- Matrix( rnorm(60), nrow = 12, ncol = 5) qr(A, pivot = T) # QR factorization of A