I first try these command, it works quite well. library(lattice) data(cuckoos) levnam <- strsplit(levels(cuckoos$species), "\\.") BUT, i want to try : levnam <- strsplit(levels(cuckoos$species), ".") to see the difference. They maybe I modified the data file, because when I try again, it says:> data(cuckoos)Warning message: data set 'cuckoos' not found in: data(cuckoos) would you please tell me how to deal with this problem? I have already tried update.packages() it doesn't help. Thanks. DJ [[alternative HTML version deleted]]