R: Return the convex hull of a triangulation object

convex.hull {interp} | R Documentation

## 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,...)

### Arguments

`tri.obj` | object of class `triSht`
`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

### Value

`x` | x coordinates of boundary nodes.
`y` | y coordinates of boundary nodes.

### Author(s)

Albrecht Gebhardt <albrecht.gebhardt@aau.at>, Roger Bivand <roger.bivand@nhh.no>

### See Also

`triSht`, `print.triSht`, `plot.triSht`, `summary.triSht`, `triangles`.

### Examples

    ## 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")

[Package interp version 1.1-1 Index]