Hello, > > The by function does not seem to allow two variables in the Indices > argument: >
Yes it does, but you must use a list of variables. (Read the help for 'by': INDICES a factor or a list of factors, each of length nrow(data).) mydata <- read.table(text=" C1 C2 C3 1 x 1 1 x 2 1 y 1 1 y 2 2 x 1 2 x 2 2 y 1 2 y 2 ", header=TRUE) last <-by(mydata, list(mydata$C1, mydata$C2), tail, n=1) last # Another way, output is more usefull. last2 <- aggregate(mydata, list(mydata$C1, mydata$C2), tail, n=1) last2[, -(1:2)] Hope this helps, Rui Barradas -- View this message in context: http://r.789695.n4.nabble.com/Selecting-obs-within-groups-defined-by-2-variables-tp4533125p4533169.html Sent from the R help mailing list archive at Nabble.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.
