tripack (version 1.3-9.2)

convex.hull: 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.

Usage

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

Value

x

x coordinates of boundary nodes.

y

y coordinates of boundary nodes.

Author

A. Gebhardt

Arguments

tri.obj

object of class "tri"

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

References

R. J. Renka (1996). Algorithm 751: TRIPACK: a constrained two-dimensional Delaunay triangulation package. ACM Transactions on Mathematical Software. 22, 1-8.

See Also

tri, print.tri, plot.tri, summary.tri, triangles, add.constraint.

Examples

# rather simple example from TRIPACK:
data(tritest)
tr<-tri.mesh(tritest$x,tritest$y)
convex.hull(tr,plot.it=TRUE)
# 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")