tripack (version 1.0-1)

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=F, add=F,...)

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=T), add to a current plot.

Value

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

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:
tr<-tri.mesh(tritest$x,tritest$y)
convex.hull(tr,plot.it=T)
# random points:
rand.tr<-tri.mesh(runif(10),runif(10))
plot(rand.tr)
rand.ch<-convex.hull(rand.tr, plot.it=T, add=T, col="red")
# use a part of the quakes data set:
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=T, add=T, col="red")

Run the code above in your browser using DataCamp Workspace