Le Fri, May 09, 2008 at 11:23:37PM -0400, Dipankar Basu a écrit : > > ex <- data.frame(id=id,year=year,x=x) > > ex1 <- subset(ex[which(ex$id=="A"|ex$id=="B"),]) > > tapply(ex1$x, ex1$id, mean) > A B C > 22.5 32.5 NA
Dear Dipankar, The reason for this behaviour is that the class of ex$id is "factor". You can avoid this by using the I command, like in: ex <- data.frame(id=I(id),year=year,x=x) Have a nice day, -- Charles Plessy http://charles.plessy.org Wakō, Saitama, Japan ______________________________________________ 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.
