

   AAdddd aann AAxxiiss ttoo aa PPlloott

        axis(side, at, labels=TRUE, ...)

   AArrgguummeennttss::

       side: an integer specifying which side of the plot the
             axis is to be drawn on.

         at: the points at which tick-marks are to be drawn.

     labels: this can either be a logical value specifying
             whether (numerical) annotations are to be made at
             the tickmarks, or a vector of character strings to
             be placed at the tickpoints.

        ...: graphical parameters may also be passed as argu-
             ments to this function.

   VVaalluuee::

        This function is invoked for its side effect, which is
        to add an axis to an already existing plot.  The axis
        is placed as follows: 1=below, 2=left, 3=above and
        4=right.

   EExxaammpplleess::

        plot(1:4, rnorm(4), axes=FALSE)
        axis(1, 1:4, LETTERS[1:4])
        axis(2)
        box() #- to make it look "as usual"

        plot(1:7, rnorm(7), type = 's', xaxt='n', col = 'red')
        axis(1, 1:7, LETTERS[1:7], col.axis = 'blue')

