>>>>> "GC" == Gray Calhoun <gray.calh...@gmail.com> >>>>> on Mon, 14 Dec 2009 19:26:44 -0600 writes:
GC> Check out crossprod and the Matrix package (capitalized); there's also GC> a discussion of their speed gains in the R newsletter that should turn GC> up with a search and in the vignette as well. Yes, use the 'Matrix' package. For the problem you mention, X being a "design matrix" of regression problem, you may be interested in the sparse.model.matrix() function which constructs such a sparse X from a formula and a data frame. With > library(Matrix) > example(sparse.model.matrix) you get a few (small sample) examples. Martin Maechler, ETH Zurich GC> -Gray GC> On Monday, December 14, 2009, parkbomee <bbom...@hotmail.com> wrote: >> >> >> Hi all, >> >> Is there a way to do a matrix multiplication in a faster way? >> I am making a product of a matrix (composed of a lot of dummy variables) and a vector, and is there any way to make it faster? >> The simple X %*% y takes too long a time. >> I know using sparse matrix would help, but don't know how to do it i R. >> >> >> Thank you. ______________________________________________ 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.