persistance of factor levels in a data frame
Hi,
Just something I don't understand:
data <- data.frame(V1=c(1:12),F1=c(rep("a",4),rep("b",4),rep("c",4)))
data_ac <- data[which(data$F1 !="b"), ]
levels(data_ac$F1)
Why the level "b" is always present ?
thanks
Tristan, R 2.0.1 for Linux Fedora 3
------------------------------------------------------------ Tristan LEFEBURE Laboratoire d'?cologie des hydrosyst?mes fluviaux (UMR 5023) Universit? Lyon I - Campus de la Doua Bat. Darwin C 69622 Villeurbanne - France Phone: (33) (0)4 26 23 44 02 Fax: (33) (0)4 72 43 15 23