I have just uploaded a package to CRAN called `gpclib' for clipping large and complex polygons. This package provides an R interface to Alan Murta's very fast General Polygon Clipper library (written in C), which has an optimized version of the Vatti algorithm. Not all features of Murta's library are implemented -- right now you can do intersections, differences, and unions. There are also functions for reading/writing from/to files and coercing between various data types. For some more details about the package see http://department.stat.ucla.edu/~rpeng/R/gpclib. Please send any comments, complaints, and bug reports to rpeng at stat.ucla.edu. Here is the DESCRIPTION file for the package: Package: gpclib Version: 1.0 Date: 1/6/2003 Depends: R (>= 1.6.1) Title: General Polygon Clipping Library for R Author: R interface by Roger D. Peng <rpeng at stat.ucla.edu>; GPC library by Alan Murta Maintainer: Roger D. Peng <rpeng at stat.ucla.edu> Description: General polygon clipping routines for R based on Alan Murta's C library License: Code written by R. D. Peng is available under the LGPL; the C code for the GPC library is free for non-commercial use (see the files `gpc.c' and `gpc.h' for details) URL: http://department.stat.ucla.edu/~rpeng/R/gpclib; http://www.cs.man.ac.uk/aig/staff/alan/software Happy clipping! -roger _______________________________ UCLA Department of Statistics rpeng at stat.ucla.edu http://www.stat.ucla.edu/~rpeng