tri.find: Locate a point in a triangulation

In interp: Interpolation Methods

Locate a point in a triangulation

Description

This subroutine locates a point P=(x,y) relative to a triangulation created by tri.mesh. If P is contained in a triangle, the three vertex indexes are returned. Otherwise, the indexes of the rightmost and leftmost visible boundary nodes are returned.

Usage

tri.find(tri.obj,x,y)

Arguments

tri.obj	an triangulation object of class triSht
x	x-coordinate of the point
y	y-coordinate of the point

Value

A list with elements i1,i2,i3 containing nodal indexes, in counterclockwise order, of the vertices of a triangle containing P=(x,y). tr contains the triangle index and bc contains the barycentric coordinates of P w.r.t. the found triangle.

If P is not contained in the convex hull of the nodes this indices are 0 (bc is meaningless then).

Author(s)

Albrecht Gebhardt <[e-mail]>, Roger Bivand <[e-mail]>

See Also

triSht, print.triSht, plot.triSht, summary.triSht, triangles, convex.hull

Examples

data(franke)
tr<-tri.mesh(franke$ds3$x,franke$ds3$y)
plot(tr)
pnt<-list(x=0.3,y=0.4)
triangle.with.pnt<-tri.find(tr,pnt$x,pnt$y)
attach(triangle.with.pnt)
lines(franke$ds3$x[c(i1,i2,i3,i1)],franke$ds3$y[c(i1,i2,i3,i1)],col="red")
points(pnt$x,pnt$y)

interp documentation built on May 29, 2024, 8:03 a.m.