On Tue, Oct 11, 2011 at 7:54 AM, ivo welch <ivo.we...@gmail.com> wrote: > hi josh---thx. I had a different version of this, and discarded it > because I think it was very slow. the reason is that on each > application, your version has to scan my (very long) data vector. (I > have many thousand different cases, too.) I presume that by() has one > scan through the vector that makes all splits.
by.data.frame() is basically a wrapper for tapply(), and the key line in tapply() is ans <- lapply(split(X, group), FUN, ...) which should be easy to adapt for mclapply. -- Thomas Lumley Professor of Biostatistics University of Auckland ______________________________________________ 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.
