convex_hull: Draw different types of convex hulls around a set of points

In markheckmann/dissertation: Functions used in dissertation

Description

Draw different types of convex hulls around a set of points

Usage

convex_hull(x, y = NULL, alpha = 0, peel = FALSE, smooth = 0,
  shape = 1, draw = TRUE, ...)

Arguments

x,y	The x and y coordinates of a set of points. Alternatively, a single argument x can be provided.
alpha	Proportion of points most distant from centroid to be removed before creating the (peeled) convex hull.
peel	Remove hull points? (useful to remove outliers, default FALSE)
smooth	Integer (1 to 3) indicating the method for creating splines around the hull.
shape	Shape parameter used for smooth=1 (see xspline for details).
draw	Draw the hull polygon (default TRUE).
...	additional parameters passed to polygon to draw the hull.

Value

A list as given by xy.coords containing the hull points is returned invisibly.

Examples

set.seed(2)
x <- rnorm(100)
y <- rnorm(100)
op <- par(mfrow=c(2,3), mar=c(3,2,3,1))

plot(x,y, main="convex hull")
convex_hull(x,y)

plot(x,y, main="colored hull")
convex_hull(x,y, col="#FF000050", density=10, angle=45, border="red")

plot(x,y, main="20% of most distant\npoints removed")
convex_hull(x,y, alpha=.2, col="#FF000050", density=10, angle=45, border="red")

plot(x,y, main="initial hull points\nremoved (peeled off)")
convex_hull(x,y, peel=T, col="#00FF0050", border="red")

plot(x,y, main="smoothed hull\n(spline interpolated)")
convex_hull(x,y, smooth=2, col="#FF000050", border="red")

plot(x,y, main="another smooting\nmethod")
convex_hull(x,y, peel=T, smooth=1, shape=1, col="#00FF0050", border="red")

par(op)

markheckmann/dissertation documentation built on May 21, 2019, 12:06 p.m.