Thank you very much. The advice I followed (and which, for some reason, I do not see here right now) was to use 'droplevels'. I needed the command for several variables at the same time, so this was very convenient.
> Hello, Have you tried 'droplevels': test <-data.frame(a=as.factor(rep(c("f1","f2","f3"),10)),b=rep(c(1,2,3),10)) test2 <- subset(test,test$a=="f1") summary(test2) a b f1:10 Min. :1 f2: 0 1st Qu.:1 f3: 0 Median :1 Mean :1 3rd Qu.:1 Max. :1 test3<-droplevels(test2) summary(test3) a b f1:10 Min. :1 1st Qu.:1 Median :1 Mean :1 3rd Qu.:1 Max. :1 A.K. > -- View this message in context: http://r.789695.n4.nabble.com/Remove-empty-levels-in-subset-tp873967p4634550.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.