plot.ashape: Plot the alpha-shape

In alphahull: Generalization of the Convex Hull of a Sample of Points in the Plane

Plot the alpha-shape

Description

This function returns a plot of the α-shape. If desired, it also adds the Delaunay triangulation and Voronoi diagram of the sample.

Usage

## S3 method for class 'ashape'
plot(x, add = FALSE, wlines = c("none", "both", "del", "vor"),
	wpoints = TRUE, number = FALSE, col = NULL, 
	xlim = NULL, ylim = NULL, lwd = NULL, ...)

Arguments

x	Object of class "ashape".
add	Logical, if TRUE add to a current plot.
wlines	"Which lines?". I.e. should the Delaunay triangulation be plotted (wlines='del'), should the Voronoi diagram be plotted (wlines='vor'), should both be plotted (wlines='both'), or none (wlines='none', the default)?
wpoints	Logical, indicates if sample points should be plotted.
number	Logical, defaulting to FALSE; if TRUE then the points plotted will be labelled with their index numbers.
col	The colour numbers for plotting the α-shape, data points, Delaunay triangulation, Voronoi diagram, and the point numbers, in that order; defaults to c(1,1,1,1,1). If fewer than five numbers are given, they are recycled. (If more than five numbers are given, the redundant ones are ignored.)
xlim	The limits on the x-axis.
ylim	The limits on the y-axis.
lwd	The line widths for plotting the tesselations and the α-shape; defaults to c(1,2).
...	Arguments to be passed to methods, such as graphical parameters (see par).

See Also

ashape.

Examples

## Not run: 
# Uniform sample of size n=300 in the annulus B(c, 0.5)\B(c, 0.25) 
# with c=(0.5, 0.5). 
n <- 300
theta<-runif(n,0,2*pi)
r<-sqrt(runif(n,0.25^2,0.5^2))
x<-cbind(0.5+r*cos(theta),0.5+r*sin(theta))
# Value of alpha
alpha <- 0.1
# alpha-shape 
ashape.obj <- ashape(x, alpha = alpha)
# Plot alpha-shape in blue, sample points in black, 
# and Delaunay triangulation in red
plot(ashape.obj, wlines= "del", col = c(4, 1, 2))

# Random sample  from a uniform distribution on a Koch snowflake 
# with initial side length 1 and 3 iterations
x <- rkoch(2000, side = 1, niter = 3)
# Value of alpha
alpha <- 0.05
# alpha-shape 
ashape.obj <- ashape(x, alpha = alpha)
# Plot alpha-shape in blue
plot(ashape.obj, col = c(4, 1))

## End(Not run)

alphahull documentation built on June 16, 2022, 5:10 p.m.