# convex.hull

0th

Percentile

##### 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.
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.

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

• 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)
quakes.tri<-tri.mesh(quakes.part$lon, quakes.part$lat, duplicate="remove")
convex.hull(quakes.tri, plot.it=T, add=T, col="red")