voronoi: Simple and weighted Voronoi tesselations

In ahb108/sparch: Assorted methods to supplement core spatial packages in R

Description

Function to produce a Voronoi tesselation (aka Dirichelet set or Thiessen polygons) from a set of point, with or without weights.

Usage

voronoi(
  x,
  ids,
  weights = NULL,
  win = NULL,
  maxdist = NULL,
  nsteps = 36,
  verbose = TRUE,
  ...
)

Arguments

x	an object of class SpatialPoints*
ids	identifiers for each point as lables for the resulting polygons
weights	optional weight values for the calculation (e.g. measure of relative ‘influence’ or ‘size’ of each point)
win	an object of class SpatialPolygons* for the exterior of the study area.
maxdist	A cut-off (the radius of a circle) for the extent of a point's tesselation.
nsteps	How many increments to use for defining the cruvature of a circle.
verbose	A logical variable indicating whether extra information on progress should be reported. Default is TRUE.

Value

An object of class SpatialPolygonsDataFrame

Examples

w <- SpatialPolygons(list( Polygons(list(Polygon(cbind(c(0,0,100,100,0), c(0,100,100,0,0)))), "1")), 1:1)
pts <- data.frame(X=runif(3)*100,Y=runif(3)*100,ptID=letters[1:3], Size=c(1,2,4))
coordinates(pts) <- ~X+Y
vor <- voronoi(pts, ids=pts$ptID, win=w)
vorw <- voronoi(pts, ids=pts$ptID, weights=pts$Size, win=w)
plot(vor, lty="dotted", border="red")
plot(vorw, border="blue", add=TRUE)
points(pts)
text(coordinates(pts)[,1],coordinates(pts)[,2], pts$Size, col="blue", adj=c(1,-1))
legend("center", lty=c("dotted","solid"),col=c("red","blue"),legend=c("unweighted","weighted"), bty="n")

ahb108/sparch documentation built on Feb. 3, 2021, 1:21 a.m.