

   TThhee NNuummbbeerr ooff LLeevveellss ooff aa FFaaccttoorr

        nlevels(x)

   DDeessccrriippttiioonn::

        `nlevels' returns the number of levels which its argu-
        ment has.  If the argument is not a `factor', `NA' is
        returned.

        The actual factor levels (if they exist) can be
        obtained with the `levels' function.

   EExxaammpplleess::

        nlevels(gl(3,7)) # = 3

