interp (version 1.1-6)

triangles: Extract a list of triangles from a triangulation object

Description

This function extracts a list of triangles from an triangulation object created by tri.mesh.

Usage

triangles(tri.obj)

Value

A matrix with columns node1, node2, node3, representing the vertex nodal indexes,

tr1, tr2, tr3, representing neighboring triangle indexes and arc1, arc2, arc3 reresenting arc indexes.

Each row represents one triangle.

Arguments

tri.obj

object of class triSht

Author

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

Details

The vertices in the returned matrix (let's denote it with retval) are ordered counterclockwise. The columns tr\(x\) and arc\(x\), \(x=1,2,3\) index the triangle and arc, respectively, which are opposite (not shared by) node node\(x\), with tri\(x=0\) if arc\(x\) indexes a boundary arc. Vertex indexes range from 1 to \(n\), the number of nodes, triangle indexes from 0 to \(nt\), and arc indexes from 1 to \(na = nt+n-1\).

See Also

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

Examples

# use the smallest Franke data set
data(franke)
fr3.tr<-tri.mesh(franke$ds3$x, franke$ds3$y)
triangles(fr3.tr)