

   xx--yy ssccaatttteerrpplloott,, ccoolloorreedd bbyy lleevveellss ooff aa ffaaccttoorr..

        plotbyfactor(x, y, f, data, col, pch, add, lg, ...)

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

          x: Variable for x axis.

          x: Variable for y axis.

          f: Factor (or variable for which as.factor() works).

       data: data frame for variables x, y, f. Default:
             sys.parent().

        col: Color numbers to use in plot. Will be replicated
             if shorter than the number of levels of the factor
             f. Default: 1:10.

        pch: Vector of plot characters. Replicated if neces-
             sary.  Default: "O".

        add: If TRUE, add to existing plot. Otherwise, create
             new plot.  Default: FALSE.

         lg: Coordinates to place a legend. Default: Missing
             (no legend).

        ...: Other graphical parameters, labels, titles e.t.c.

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

        > plotbyfactor(petal.wid,petal.len,species,data=iris)

