Lefebure Tristan wrote:
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
You must explicitly drop unused levels of a factor created by subsetting.
> levels(data_ac$F1[drop = TRUE])
[1] "a" "c"
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