## S4 method for signature 'SpatialPolygons,SpatialPolygons'
symdif(x, y, ...)

#SpatialPolygons
if (require(rgdal) & require(rgeos)) {
	p <- shapefile(system.file("external/lux.shp", package="raster"))
	b <- as(extent(6, 6.4, 49.75, 50), 'SpatialPolygons')
	crs(b) <- crs(p)
	sd <- symdif(p, b)
	plot(sd, col='red')
}