interp (version 1.0-33)

tri.mesh: Delaunay triangulation

Description

This function generates a Delaunay triangulation of arbitrarily distributed points in the plane. The resulting object can be printed or plotted, some additional functions can extract details from it like the list of triangles, arcs or the convex hull.

Usage

tri.mesh(x, y = NULL, duplicate = "error")

Arguments

x

vector containing \(x\) coordinates of the data. If y is missing x should be a list or dataframe with two components x and y.

y

vector containing \(y\) coordinates of the data. Can be omitted if x is a list with two components x and y.

duplicate

flag indicating how to handle duplicate elements. Possible values are:

  • "error" -- default,

  • "strip" -- remove all duplicate points,

  • "remove" -- leave one point of the duplicate points.

Value

an object of class "triSht", see triSht.

Details

This function creates a Delaunay triangulation of a set of arbitrarily distributed points in the plane referred to as nodes.

The Delaunay triangulation is defined as a set of triangles with the following five properties:

  1. The triangle vertices are nodes.

  2. No triangle contains a node other than its vertices.

  3. The interiors of the triangles are pairwise disjoint.

  4. The union of triangles is the convex hull of the set of nodes (the smallest convex set which contains the nodes).

  5. The interior of the circumcircle of each triangle contains no node.

The first four properties define a triangulation, and the last property results in a triangulation which is as close as possible to equiangular in a certain sense and which is uniquely defined unless four or more nodes lie on a common circle. This property makes the triangulation well-suited for solving closest point problems and for triangle-based interpolation.

This triangulation is based on the s-hull algorithm by David Sinclair. It consist of two steps:

  1. Create an initial non-overlapping triangulation from the radially sorted nodes (w.r.t to an arbitrary first node). Starting from a first triangle built from the first node and its nearest neigbours this is done by adding triangles from the next node (in the sense of distance to the first node) to the hull of the actual triangulation visible from this node (sweep hull step).

  2. Apply triange flipping to each pair of triangles sharing a border until condition 5 holds (Cline-Renka test).

This algorithm has complexicity \(O(n*log(n))\).

References

B. Delaunay, Sur la sphere vide. A la memoire de Georges Voronoi, Bulletin de l'Academie des Sciences de l'URSS. Classe des sciences mathematiques et na, 1934, no. 6, p. 793--800

D. A. Sinclair, S-Hull: A Fast Radial Sweep-Hull Routine for Delaunay Triangulation. https://arxiv.org/pdf/1604.01428.pdf, 2016.

See Also

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

Examples

Run this code
# NOT RUN {
## use Frankes datasets:
data(franke)
tr1 <- tri.mesh(franke$ds3$x, franke$ds3$y)
tr1
tr2 <- tri.mesh(franke$ds2)
summary(tr2)
# }

Run the code above in your browser using DataCamp Workspace