levels attribute of
object are pruned to contain
only the levels occurring in the factor.
pruneLevels(object)
factor.
object, but with the
levels
attribute containing only value occurring in the factor.
f1 <- factor(c(1,1,2,3,3,4,5)) levels(f1) f2 <- f1[4:7] levels(f2) levels(pruneLevels(f2))