dgeqrf {bigalgebra} R Documentation

## QR factorization

### Description

DGEQRF computes a QR factorization of a real M-by-N matrix A: A = Q * R.

### Usage

dgeqrf(
M = NULL,
N = NULL,
A,
LDA = NULL,
TAU = NULL,
WORK = NULL,
LWORK = NULL
)


### Arguments

 M an integer. The number of rows of the matrix A. M >= 0. N an integer. The number of columns of the matrix A. N >= 0. A the M-by-N big matrix A. LDA an integer. The leading dimension of the array A. LDA >= max(1,M). TAU a min(M,N) matrix. The scalar factors of the elementary reflectors. WORK a (MAX(1,LWORK)) matrix. On exit, if INFO = 0, WORK(1) returns the optimal LWORK. LWORK an integer. The dimension of th array WORK.

### Value

M-by-N big matrix A. The elements on and above the diagonal of the array contain the min(M,N)-by-N upper trapezoidal matrix R (R is upper triangular if m >= n); the elements below the diagonal, with the array TAU, represent the orthogonal matrix Q as a product of min(m,n) elementary reflectors.

### Examples

## Not run:
#' hilbert <- function(n) { i <- 1:n; 1 / outer(i - 1, i, "+") }
h9 <- hilbert(9); h9
qr(h9)$rank #--> only 7 qrh9 <- qr(h9, tol = 1e-10) qrh9$rank
C <- as.big.matrix(h9)
dgeqrf(A=C)

# The big.matrix file backings will be deleted when garbage collected.
rm(C)
gc()

## End(Not run)


[Package bigalgebra version 1.1.1 Index]