[R] Add text/numbers to x axis?

[Robert Lundqvist]

Is there any simple way to add text to the x axis in R? I have tried to
add simple characters in R without any greater sucess. As an example of
what I want to do is the added C in the following "dumb" plot (produced
with MacAnova using the option "dumb:T"):

    ++------+-------+------+-------+------+-------+------+-------++
   1+                              :                             *+
    |                              :                       *  *   |
    |                              :                 *  *         |
    |                              :              *  .            |
 0.8+                              :           *     .            +
    |                              :                 .            |
    |                              :        *        .            |
    |                              :     *           .            |
 0.6+                              :                 .            +
    |                              :  *              .            |
    |                              *                 .            |
    |                              :                 .            |
    |                           *  :                 .            |
 0.4+                              :                 .            +
    |                        *     :                 .            |
    |                     *        :                 .            |
    |                              :                 .            |
 0.2+                  *           :                 .            +
    |               *              :                 .            |
    |         *  *                 :                 .            |
    |*  *  *                       :                 .            |
   0++------+-------+------+-------+------+-------+--.---+-------++
    -2    -1.5     -1    -0.5      0     0.5      1  C  1.5      2


My attempts to use locator() and text() in R's plot() has not been working
as good as expected. Never really knows where the added symbols end up...

BTW, anyone who knows how such "dumb" plots could be achieved in R? This
option is avaliable in S, so a port to R shouldn't be impossible, should
it? Don't know how to do it myself however...

Robert