plot.ashape {alphahull}R Documentation

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

# Uniform sample of size n=300 in the disc B(c,0.5)\B(c,0.25) 
# with c=(0.5,0.5). 
n<-300
m<-0
data<-matrix(0,n,2)
while(m<n){
x<-runif(1)
y<-runif(1)
if(((x-0.5)^2+(y-0.5)^2<=(0.5)^2 )&((x-0.5)^2+(y-0.5)^2>=(0.25)^2)){
m<-m+1
data[m,]<-c(x,y)
}
}
# Value of alpha
alpha<-0.1
# alpha-shape 
ashape.obj<-ashape(data,alpha=alpha)
# Plot alpha-shape in red and Delaunay triangulation in black
plot(ashape.obj)

[Package alphahull version 0.1 Index]