convex.hull

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Return the convex hull of a triangulation object

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

  • xx coordinates of boundary nodes.
  • yy 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.

Aliases
  • convex.hull
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")
Documentation reproduced from package tripack, version 1.0-1, License: R functions: GPL, Fortran code: available at netlib

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