Calculates the Voronoi (Dirichlet) tesselation for a set of points. 

Depends on the R-package deldir:
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The function "deldir" computes the Delaunay triangulation (and hence the 
Dirichlet tesselation) of a planar point set according to the second 
(iterative) algorithm of Lee and Schacter (1980). The triangulation is made to 
be with respect to the whole plane by suspending it from so-called ideal points 
(-Inf,-Inf), (Inf,-Inf) (Inf,Inf), and (-Inf,Inf). The triangulation is also 
enclosed in a finite rectangular window. A set of dummy points may be added, 
in various ways, to the set of data points being triangulated.

Reference
Lee, D.T., and Schacter, B.J. 1980. Two algorithms for constructing a 
Delaunay triangulation. International Journal of Computer and Information 
Sciences 9(3): 219–242.

