Internal deldir functions
Construct the Delaunay triangulation and the Dirichlet
(Voronoi) tessellation of a planar point set.
Produce a plot of the Delaunay triangulation and Dirichlet (Voronoi)
tesselation of a planar point set, as constructed by the function deldir.
Plot Dirchlet/Voronoi tiles
Compute centroids of Voronoi/Dirchlet tiles.
Create a list of tiles in a tessellation.