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Union all subpolygons of a "SpatialPolygons" object. This is a wrapper for the polygon clipping engines implemented by packages rgeos and polyclip.


unionSpatialPolygons(SpP, method = c("rgeos", "polyclip"), ...)



an object of class "SpatialPolygons". For the polyclip method only, all polygon classes for which an xylist-method exists should work as input.


polygon clipping machinery to use. Default is to simply call gUnaryUnion in package rgeos. For method="polyclip", function polyclip from package polyclip is used. The alternative method="gpclib" via package maptools is no longer provided in surveillance > 1.20.3.


further arguments passed to the chosen method.


an object of class

"SpatialPolygons" representing the union of all subpolygons.


Sebastian Meyer

See also

gUnaryUnion in package rgeos, polyclip in package polyclip.


## Load districts of Germany
load(system.file("shapes", "districtsD.RData", package = "surveillance"))
plot(districtsD, border = "gray", asp = 1)  

## Union these districts using either "rgeos" or "polyclip"
if (requireNamespace("rgeos"))  {
    stateD <- unionSpatialPolygons(districtsD, method = "rgeos")
    plot(stateD, add = TRUE, border = 2, lwd = 2)
if (requireNamespace("polyclip")) {
    stateD_pc <- unionSpatialPolygons(districtsD, method = "polyclip")
    plot(stateD_pc, add = TRUE, border = 1, lwd = 2, lty = 2)