facmul {Matrix} | R Documentation |
Performs multiplication by factors for certain decompositions (and allows explicit formation of those factors).
facmul(x, factor, y, transpose, left, ...)
x |
a matrix decomposition. No missing values or IEEE special values are allowed. |
factor |
an indicator for selecting a particular factor for multiplication. |
y |
a matrix or vector to be multiplied by the factor or its transpose. No missing values or IEEE special values are allowed. |
transpose |
a logical value. When FALSE (the default) the factor is
applied. When TRUE the transpose of the factor is applied.
|
left |
a logical value. When TRUE (the default) the factor is
applied from the left. When FALSE the factor is applied
from the right.
|
... |
the method for "qr.Matrix" has additional arguments.
|
the product of the selected factor (or its transpose) and y
Factors for decompositions such as lu
and qr
can be
stored in a compact form.
The function facmul
allows multiplication without explicit
formation of the factors, saving both storage and operations.
Golub, G., and Van Loan, C. F. (1989). Matrix Computations, 2nd edition, Johns Hopkins, Baltimore.
library(Matrix) x <- Matrix(rnorm(9), 3, 3) ## Not run: qrx <- qr(x) # QR factorization of x y <- rnorm(3) facmul( qr(x), factor = "Q", y) # form Q y ## End(Not run)