[R] List seems to drop empty levels of factors when containing them
andrewr at uidaho.edu
Wed Nov 10 04:43:52 CET 2004
Greetings R community,
I am curious about the following behaviour: if I define a factor, and
then store a subset of it in a list, the stored version seems to drop
levels that were not included in the subset. E.g. ..
> mask <- c(T, F)
> grp.1 <- factor(c(1,2))
 1 2
Levels: 1 2
It is as though the list were redefining the factor and dropping
empty levels. I would like to keep them (I am using the list for a
two-dimensional tapply). Is there any way to avoid this?
I'm using R 2.0.0 on FreeBSD 5.2.1.
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