

   CCoommppuuttee FFaaccttoorr IInntteerraaccttiioonnss

        interaction(..., drop=FALSE)

   AArrgguummeennttss::

        ...: The factors for which interaction is to be com-
             puted.

       drop: If `drop' is `TRUE', empty factor levels are
             dropped from the result. The default is to retain
             all factor levels.

   DDeessccrriippttiioonn::

        `interaction' computes a factor which represents the
        interaction of the given factors.  The result of
        `interaction' is always unordered.

   VVaalluuee::

        A factor which represents the interaction of the given
        factors.

   SSeeee AAllssoo::

        `factor'.

   EExxaammpplleess::

        a <- gl(2, 2, 8)
        b <- gl(2, 4, 8)
        interaction(a, b)

