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 |
left |
a logical value. When |
... |
the method for |
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)