voronoifortune (version 1.0)

plot.voronoi: Plot Voronoi Tessellation and Delaunay Triangulation

Description

Plot Voronoi tessellation (VT) and Delaunay triangulation (DT).

Usage

# S3 method for voronoi
plot(x, delaunay = TRUE, voronoi = TRUE,
     X = NULL, add = FALSE, asp = 1,
     col.delaunay = "red", col.voronoi = "blue", ...)

Value

(NULL).

Arguments

x

an object of class "voronoi".

delaunay

a logical value: draw the DT?

voronoi

a logical value: draw the VT?

X

a two-column matrix with the original data (site coordinates).

add

a logical value. By default, a new plot is made. Setting add = TRUE is useful to add the tessellation and/or the triangulation on, e.g., a map.

asp

a numeric value. By default, both axes are scaled similarly (isometry). Use asp = NULL to have independent scaling on both axes (like a standard plot in R).

col.delaunay, col.voronoi

the colours used for the segments.

...

other arguments passed to plot.default.

Author

Emmanuel Paradis

Details

The ... argument makes plotting very flexible.

The default procedure is to first draw the DT, setting the limits of the axes according to the data, and then to draw the VT. Playing with the different options can change the order these two are drawn.

The Fortune algorithm often adds some vertices which are far from the data points (sites); so if delaunay = FALSE, the scales are likely to extend much more than the default.

The infinite edges of the VT are drawn as dashed lines.

See Also

voronoi

Examples

X <- matrix(runif(200), 100, 2)
res <- voronoi(X)
plot(res)
plot(res, delaunay = FALSE)

dat <- matrix(runif(40), 20, 2)
tess.dat <- voronoi(dat)
op <- par(mar = rep(0, 4))
## pass the data with the X argument:
plot(tess.dat, X = dat, pch = ".", axes = FALSE, ann = FALSE,
     xlim = c(-1, 2), ylim = c(-1, 2))
legend("topleft", , c("Delaunay triangulation", "Voronoi tessellation"),
       lty = 1, col = c("red", "blue"), bty = "n")
par(op)