

   DDrraaww FFuunnccttiioonn PPlloottss

        curve(expr, from, to, n=101, ...)

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

       expr: an expression, written as a function of `x' which
             will be plotted.

    from,to: the range over which the function will be plotted.

          n: the expression will be evaluated at `n' points
             equally spaced over the range `[from, to]'.  The
             points determined in this way are then joined with
             straight lines.

        ...: graphical parameters can also be specified as
             arguments.

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

        This function draws a curve corresponding to the given
        expression (in `x') over the interval `[from,to]'.  It
        is a quick hack which seems to serve a useful purpose,
        but can give bad results for functions which are dis-
        continuous.

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

        `NULL'.  For ``expensive'' `expr'essions, you should
        smarter tools.

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

        `splinefun' for spline interpolation, `lines'.

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

        curve(x^3-3*x, -2, 2)
        curve(x^2-2, add = TRUE, col = "violet")

