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... > ## your answers will be in the aa and bb columns > result <- transform(m, aa=a.x * a.y, bb=b.x * b.y) > > ==== > > Truth be told, if you use normal data.frames, the code will look very > similar to above, so you can try that, too. > > HTH, > -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 -- Dimitri Liakhovitski marketfusionanalytics.com ______________________________________________ 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.