One possibility: n.A<-nrow(A) n.B<-nrow(B)
abs( kronecker(A,rep(1,n.B)) - kronecker(rep(1,n.A),B) ) -tgs On Sat, May 22, 2010 at 3:20 PM, Shi, Tao <shida...@yahoo.com> wrote: > 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. > [[alternative HTML version deleted]] ______________________________________________ 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.
