rgeos (version 0.6-4)

gDelaunayTriangulation: Compute Delaunay triangulation between points

Description

Function to compute the Delaunay triangulation between points; only available for GEOS >= 3.4.0.

Usage

gDelaunayTriangulation(spgeom, tolerance=0.0, onlyEdges=FALSE)

Value

Either a SpatialPolygons object or a SpatialLines object containing a single Lines object of the undirected edges in the triangulation.

Arguments

spgeom

sp points object as defined in package sp

tolerance

Numerical tolerance value to be used in triangulation

onlyEdges

Logical, default returns triangles as polygons, if TRUE, returns a SpatialLines object with a single MULTILINESTRING

Author

Roger Bivand

Details

When onlyEdges is TRUE, the SpatialLines object may be de-merged to identify the input points that are touched by each edge, making it possible to identify spatial neighbours.

References

https://en.wikipedia.org/wiki/Delaunay_triangulation

Examples

if (version_GEOS0() > "3.4.0") {
library(sp)
data(meuse)
coordinates(meuse) <- c("x", "y")
plot(gDelaunayTriangulation(meuse))
points(meuse)
out <- gDelaunayTriangulation(meuse, onlyEdges=TRUE)
lns <- slot(slot(out, "lines")[[1]], "Lines")
out1 <- SpatialLines(lapply(seq(along=lns), function(i) Lines(list(lns[[i]]),
 ID=as.character(i))))
out2 <- lapply(1:length(out1), function(i) which(gTouches(meuse, out1[i],
 byid=TRUE)))
out3 <- do.call("rbind", out2)
o <- order(out3[,1], out3[,2])
out4 <- out3[o,]
out5 <- data.frame(from=out4[,1], to=out4[,2], weight=1)
head(out5)
if (FALSE) {
if (require(spdep)) {
class(out5) <- c("spatial.neighbour", class(out5))
attr(out5, "n") <- length(meuse)
attr(out5, "region.id") <- as.character(1:length(meuse))
nb1 <- sn2listw(out5)$neighbours
nb2 <- make.sym.nb(nb1)
}
}
}