surveillance (version 1.12.1)

unionSpatialPolygons: Compute the Unary Union of "SpatialPolygons"

Description

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

Usage

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

Arguments

SpP

an object of class "SpatialPolygons". For the polyclip method only, all polygon classes for which an

method

polygon clipping machinery to use. Default is to simply call gUnaryUnion in package rgeos. For method="polyclip", function

...

further arguments passed to the chosen method.

Value

• an object of class "SpatialPolygons" representing the union of all subpolygons.

See Also

gUnaryUnion in package rgeos, polyclip in package polyclip, unionSpatialPolygons in package maptools (for using union of package gpclib).

Examples

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

## 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)
}