Compute the Unary Union of "SpatialPolygons"
unionSpatialPolygons.Rd
Union all subpolygons of a
"SpatialPolygons"
object.
This is a wrapper for the polygon clipping engines implemented by
packages rgeos and polyclip.
Usage
unionSpatialPolygons(SpP, method = c("rgeos", "polyclip"), ...)
Arguments
- SpP
an object of class
"SpatialPolygons"
. For the polyclipmethod
only, all polygon classes for which anxylist
-method exists should work as input.- method
polygon clipping machinery to use. Default is to simply call
gUnaryUnion
in package rgeos. Formethod="polyclip"
, functionpolyclip
from package polyclip is used. The alternativemethod="gpclib"
via package maptools is no longer provided in surveillance > 1.20.3.- ...
further arguments passed to the chosen
method
.
See also
gUnaryUnion
in package rgeos,
polyclip
in package polyclip.
Examples
## 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)
}