convex.hull: Return the convex hull of a triangulation object

In interp: Interpolation Methods

Return the convex hull of a triangulation object

Description

Given a triangulation tri.obj of n points in the plane, this subroutine returns two vectors containing the coordinates of the nodes on the boundary of the convex hull.

ConvexHull is an experimental C++ implementation of Grahams Scan without previous triangulation, should be much faster.

Usage

convex.hull(tri.obj, plot.it=FALSE, add=FALSE,...)
       ConvexHull(x,y)

Arguments

tri.obj	object of class triSht
plot.it	logical, if TRUE the convex hull of tri.obj will be plotted.
add	logical. if TRUE (and plot.it=TRUE), add to a current plot.
...	additional plot arguments
x	only for ConvexHull(): x coordinates for C++ call to ConvexHull
y	only for ConvexHull(): see x

Value

x	x coordinates of boundary nodes.
y	y coordinates of boundary nodes.

Author(s)

Albrecht Gebhardt <[e-mail]>, Roger Bivand <[e-mail]>

See Also

triSht, print.triSht, plot.triSht, summary.triSht, triangles.

Examples

## random points:
rand.tr<-tri.mesh(runif(10),runif(10))
plot(rand.tr)
rand.ch<-convex.hull(rand.tr, plot.it=TRUE, add=TRUE, col="red")
## use a part of the quakes data set:
data(quakes)
quakes.part<-quakes[(quakes[,1]<=-17 & quakes[,1]>=-19.0 &
                     quakes[,2]<=182.0 & quakes[,2]>=180.0),]
quakes.tri<-tri.mesh(quakes.part$lon, quakes.part$lat, duplicate="remove")
plot(quakes.tri)
convex.hull(quakes.tri, plot.it=TRUE, add=TRUE, col="red")

interp documentation built on Nov. 28, 2023, 1:07 a.m.