Truncating polygons in R

Hi,

I am trying to create polygons around a set of points within a 1*1 square to
cover the whole square.  I do not have access to a GIS based package, so I
can really only use R to do this work.

I have been creating polygons around the points using the commands
voronoi.mosaic and voronoi.polygon commands from the tripack package.  I can
then convert the polygons to a spatial polygon data frame so I can use the
polygons for other things, but I am finding that my polygons extend beyond
the boundaries of the 1*1 square.  Is there any command I can use in R to
truncate the polygons so that they don't extend beyond the boundary using
either the voronoi polygons or the spatial polygons?  Or is there a better
way to create the polygons?

Any help would be greatly appreciated.

Regards,

Sandy Burden
School of Mathematics and Applied Statistics,
University of Wollongong
sburden at uow.edu.au