

   PPrruunnee FFaaccttoorr LLeevveellss

        pruneLevels(object)

   AArrgguummeennttss::

     object: an object inheriting from class `factor'.

   DDeessccrriippttiioonn::

        The `levels' attribute of `object' are pruned to con-
        tain only the levels occurring in the factor.

   VVaalluuee::

        an object identical to `object', but with the `levels'
        attribute containing only value occurring in the fac-
        tor.

   AAuutthhoorr((ss))::

        Jose Pinheiro and Douglas Bates

   SSeeee AAllssoo::

        `factor', `link{ordered}'

   EExxaammpplleess::

        library(lme)
        f1 <- factor(c(1,1,2,3,3,4,5))
        levels(f1)
        f2 <- f1[4:7]
        levels(f2)
        levels(pruneLevels(f2))

