

   FFaaccttoorr CCooddeess

        codes(x)
        codes(x) <- value

   DDeessccrriippttiioonn::

        This (generic) function returns a numeric coding of a
        factor. It can also be used to assign to a factor using
        the coded form.

   VVaalluuee::

        For an ordered factor, it returns the internal coding
        (1 for the lowest group, 2 for the second lowest,
        etc.). For an unordered factor, an alphabetical order-
        ing of the levels is assumed, i.e the level that is
        coded 1 is the one whose name is sorted first according
        to the prevailing collating sequence.

   NNoottee::

        The behaviour for unordered factors is dubious, but
        compatible with S version 3. To get the internal coding
        of a factor, use `as.integer'. Note in particular that
        the codes may not be the same in different language
        locales because of collating differences.

   SSeeee AAllssoo::

        `unclass' is very similar if applied to factors; `fac-
        tor', `levels', `nlevels'.

   EExxaammpplleess::

        codes(rep(factor(c(20,10)),3))

        x <- gl(3,5)
        codes(x)[3] <- 2
        x

        data(esoph)
        ( ag <- esoph$alcgp[12:1] )
        codes(ag)

        codes(factor(1:10)) # BEWARE!

