

   LLeevveellss AAttttrriibbuutteess

        levels(x)
        levels(x) <- value

   DDeessccrriippttiioonn::

        `levels' provides access to the levels attribute of a
        variable.  The first form returns the value of the lev-
        els of its argument and the second sets the attribute.

        The assignment for of `levels' is a generic function
        and new methods can be written for it.  The most impor-
        tant method is that for factors.

   SSeeee AAllssoo::

        `levels<-.factor', `nlevels'.

