To create a nice bounded Voronoi polygons tessellation of a point layer
in R, we need two libraries: sp and deldir. The following function
takes a SpatialPointsDataFrame as input, and returns a
SpatialPolygonsDataFrame that represents the Voronoi tessellation of
the input point layer.
voronoipolygons = function(layer) {
require(deldir)
crds = layer@coords
z = deldir(crds[,1], crds[,2])
w = tile.list(z)
polys = vector(mode='list', length=length(w))
require(sp)
for (i in seq(along=polys)) {
pcrds = cbind(w[[i]]$x, w[[i]]$y)
pcrds = rbind(pcrds, pcrds[1,])
polys[[i]] = Polygons(list(Polygon(pcrds)), ID=as.character(i))
}
SP = SpatialPolygons(polys)
voronoi = SpatialPolygonsDataFrame(SP, data=data.frame(x=crds[,1],
y=crds[,2], row.names=sapply(slot(SP, 'polygons'),
function(x) slot(x, 'ID'))))
}
To save the output to shapefile, simply usewriteOGR from the rgdal
library:
library(rgdal)
?writeOGR
