tripack (version 1.3-9.2)

on.convex.hull: Determines if points are on the convex hull of a triangulation object

Description

Given a triangulation tri.obj of \(n\) points in the plane, this subroutine returns a logical vector indicating if the points \((x_i,y_i)\) lay on the convex hull of tri.obj.

Usage

on.convex.hull(tri.obj, x, y)

Value

Logical vector.

Author

A. Gebhardt

Arguments

tri.obj

object of class "tri"

x

vector of x-coordinates of points to locate

y

vector of y-coordinates of points to locate

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, convex.hull, in.convex.hull.

Examples

# example from TRIPACK:
data(tritest)
tr<-tri.mesh(tritest$x,tritest$y)
on.convex.hull(tr,0.5,0.5)
on.convex.hull(tr,c(0.5,-1,1),c(0.5,1,1))
# use a part of the quakes data set:
data(quakes)
quakes.part<-quakes[(quakes[,1]<=-10.78 & quakes[,1]>=-19.4 &
                     quakes[,2]<=182.29 & quakes[,2]>=165.77),]
q.tri<-tri.mesh(quakes.part$lon, quakes.part$lat, duplicate="remove")
on.convex.hull(q.tri,quakes.part$lon[1:20],quakes.part$lat[1:20])