Re: Removing levels from a factor

[Gregor Gorjanc <gregor.gorjanc@bfro.uni-lj.si>]

Douglas Bates <bates <at> stat.wisc.edu> writes:
...
> 
> However, as far as I can tell no one answered the original question
> which was how do you drop unused levels from a factor - assuming that
> you do not want to do this by banishing the concept of a factor and
> exiling any person who dares to speak the name. The answer in R, and I
> believe also in S-PLUS, is to use drop = TRUE in a subscripting
> expression.  Thus

There is also drop.levels() function in gdata package for R - I am not
sure if it is also in S-PLUS port. I use it often. Usually I import the
data, check the structure with str(), occasionally I remove some data
and then unused levels come up. Use of drop.levels() after data handling
saved me a lot of "problems" later on.

Gregor