Hi, when I use use subset in a data.frame, all empty levels are maintained in the new table.
> test <- data.frame(a=as.factor(rep(c("f1","f2","f3"),10)),b=rep(c(1,2,3),10)) > summary(test) a b f1:10 Min. :1 f2:10 1st Qu.:1 f3:10 Median :2 Mean :2 3rd Qu.:3 Max. :3 > 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 Look that the f2 and f3 are in the new table, how to remove all empty levels? Thanks Ronaldo [[alternative HTML version deleted]] ______________________________________________ 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.