Reconstruct the Q, R, or X Matrices from a QR Object

DESCRIPTION:

Returns the original matrix from which the object was constructed.

USAGE:

qr.X(qrstr, complete=F, ncol=) 
qr.Q(qrstr, complete=F, Dvec=1) 
qr.R(qrstr, complete=F) 

REQUIRED ARGUMENTS:

qrstr
object representing a QR decomposition. This will typically have come from a previous call to qr or lsfit.

OPTIONAL ARGUMENTS:

complete
logical expression of length 1. Indicates whether an arbitrary orthogonal completion of the Q or X matrices is to be made, or whether the R matrix is to be completed by binding zero-value rows beneath the square upper triangle.
ncol
integer in the range 1:nrow(qrstr$qr). The number of columns to be in the reconstructed X. The default when complete==F is the original X from which the qr object was constructed. The default when complete==T is a square matrix with the original X in the first ncol(X) columns and an arbitrary orthogonal completion (unitary completion in the complex case) in the remaining columns.
Dvec
vector (not matrix) of diagonal values. Each column of the returned Q will be multiplied by the corresponding diagonal value.

VALUE:

qr.X returns X, the original matrix from which the qr object was constructed. If complete==T or the argument ncol is greater than ncol(X) , additional columns from an arbitrary orthogonal (unitary) completion of X are returned.
qr.Q returns Q, the order- nrow(X) orthogonal (unitary) transformation represented by qrstr. If complete==T, Q has nrow(X) columns. If complete==F , Q has ncol(X) columns. When Dvec is specified, each column of Q is multiplied by the corresponding value in Dvec.
qr.R returns R, the c(ncol(X),ncol(X)) upper triangular matrix such that X == Q %*% R. If complete==T, R has nrow(X) rows. If complete==F , R has ncol(X) rows.

SEE ALSO:

, .

EXAMPLES:

qrstr <- qr(x)      # dim(x) == c(n,p) 
Q <- qr.Q(qrstr) # dim(Q) == dim(x) 
R <- qr.R(qrstr) # dim(R) == ncol(x) 
X <- qr.X(qrstr) # X == x 
# X == Q %*% R 
Qc <- qr.Q(qrstr, complete=T) # dim(Qc) == nrow(x) 
QD <- qr.Q(qrstr, D=seq(p))   # QD == Q %*% diag(D) 
Rc <- qr.R(qrstr, complete=T) # dim(Rc) == dim(x) 
Xc <- qr.X(qrstr, complete=T) # Xc[,seq(p)]==x ; dim(Xc)==nrow(x)