[R] groups of boxplots

[Marc Schwartz]

Katalin Csillery wrote:
> Hi,
> 
> does anyone know how to make pairs of boxplots? E.g. 5 pairs of boxes. I
> figured a not very elegant way, by inserting a dummy NA field to the list
> where the data is given. So, where I have the dummy I got more distance
> between boxes, as a result it looks like groups. But I am having problems
> with putting the names under the groups, and the thick marks.
> 
> Any better idea?
> Thanks, Kati
> ___
> Katalin Csillery
> Division of Biological Sciences
> University of Montana, Missoula MT 59801
> Phone: 406 243 6106, E-mail: csillery at selway.umt.edu
> ----------------------------------------------------

Use the 'add' and 'at' arguments to boxplot().

Better yet, look at the last example in ?boxplot

For the labels, use the midpoints of the pairs of 'at' values for 
mtext().  See ?mtext for more details.

Regards,

Marc Schwartz