R: Plot the alpha-shape

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

    ## 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)

[Package alphahull version 2.2 Index]