alphahull (version 2.5)

plot.ashape: Plot the alpha-shape

Description

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

Usage

# S3 method for 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 \(\alpha\)-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 \(\alpha\)-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))
# }