Hi, On Wed, Jan 11, 2012 at 10:50 AM, Dimitri Liakhovitski <dimitri.liakhovit...@gmail.com> wrote: > Thanks a lot, Steve. I have one question (below): > > >> ==== >> library(data.table) >> >> ## your data >> xx <- data.table(group=c(rep("group1",5),rep("group2",5)), >> a=1:10, b=seq(10,100,by=10), key="group") >> yy <- data.table(group=c("group1","group2"), a=c(10,20), b=c(2,3), >> key="group") >> >> ## temp data.table to get your ducks in a row >> m <- merge(xx, yy, by="group", suffixes=c(".x", ".y")) > > > Dimitri: The step above (merge) - I was thinking of it but decided > against it because my xx already fills up tons of memory. When I merge > xx and yy that doubles the number of variables - I am afraid my memory > won't hold that much stuff...
Fair enough ... how about just using `match`, then, ie: R> aa <- x$a * y$a[match(x$group, y$group)] Should do the trick, no? -steve -- Steve Lianoglou Graduate Student: Computational Systems Biology | Memorial Sloan-Kettering Cancer Center | Weill Medical College of Cornell University Contact Info: http://cbio.mskcc.org/~lianos/contact ______________________________________________ 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.