drop.levels {gdata} | R Documentation |
Drop unused levels in a factor.
drop.levels(x, reorder=TRUE, ...)
x |
object to be processed |
reorder |
should factor levels be reordered using
reorder.factor ? |
... |
additional arguments to reorder.factor |
drop.levels
is a generic function, where default method does
nothing, while method for factor s
drops all unused levels. There
are also convinient methods for list
and data.frame
, where
all unused levels are droped in all factors (one by one) in a
list
or a data.frame
.
a data frame
Jim Rogers james.a.rogers@pfizer.com
f <- factor(c("A", "B", "C", "D"))[1:3] drop.levels(f) l <- list(f=f, i=1:3, c=c("A", "B", "D")) drop.levels(l) df <- as.data.frame(l) str(df) str(drop.levels(df))