One way to do it: apply(B, 1, function(x) t(apply(A, 1, function(y) abs(y-x) )) )
----- Original Message ---- > From: David Neu <da...@davidneu.com> > To: r-help@r-project.org > Sent: Sat, May 22, 2010 10:35:32 AM > Subject: [R] Fast Matrix Computation > > Hi, I have two (large) matrices A and B of dimensions (m,n) and (p,n) > respectively. I'd like to see if the is a fast way to compute a new > matrix C with dimension (m*p,n) in which each row in C is found by applying > some function f to each pair of rows (x,y) where x is a row in A and y is > a row in B. For example, if A <- matrix(c(1, 2, 3, 4, 5, 6), > byrow=TRUE, ncol=3) B <- matrix(c(7, 8, 9), byrow=TRUE, ncol=3) and > f <- function(x,y) abs(y-x) then C <- matrix(c(6, 6, 6, 3, > 3, 3), byrow=TRUE, ncol=3) Many > thanks! Cheers, David ______________________________________________ > ymailto="mailto:R-help@r-project.org"; > href="mailto:R-help@r-project.org";>R-help@r-project.org mailing list > href="https://stat.ethz.ch/mailman/listinfo/r-help"; target=_blank > >https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting > guide http://www.R-project.org/posting-guide.html and provide commented, > minimal, self-contained, reproducible code. ______________________________________________ R-help@r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code.
