This library contains an R implementation of some triangulation routines.  

It is based on Fortran code from R. J. Renka in the ACM Collected 
Algorithms archive under

  http://www.netlib.org/toms/751

  R. J. Renka (1996). Algorithm 751: TRIPACK: a constrained
  two-dimensional {Delaunay} triangulation package.
  ACM Transactions on Mathematical Software.
  22, 1-8.

I added the Fortran files inhull.f and voronoi.f wich implements additional
subroutines for determination of convex hulls and voronoi mosaics.

Currently the library  contains the following R functions which provide access
to the Fortran subroutines of TRIPACK and implements new objects for triangu-
lations and voronoi mosaics:

add.constraint           
convex.hull             
identify.tri           
in.convex.hull        
neighbours          
on.convex.hull     
outer.convhull   
plot.tri       
plot.voronoi  
print.summary.tri        
print.summary.voronoi   
print.tri              
print.tri            
summary.tri         
summary.voronoi    
tri               
tri.find         
tri.mesh        
triangles      
voronoi      
voronoi.mosaic

The help pages are based on the Fortran comments. 

This library was intended by the akima library, which also contains some (but 
not all) of the TRIPACK functions. 

Currently plots of voronoi mosaics may fail (due to numerical problems) if 
the corresponding triangulation contains very small triangles at the boundary.

------------------------------------------------------------------
Albrecht Gebhardt           email: albrecht.gebhardt@uni-klu.ac.at
Institut fuer Mathematik    Tel. : (++43 463) 2700/837
Universitaet Klagenfurt     Fax  : (++43 463) 2700/834
Villacher Str. 161
A-9020 Klagenfurt, Austria
------------------------------------------------------------------

The abstract of the original article at ACM follows:
##############################################################################
                 TRIPACK is a Fortran 77 software package that employs
                 an incremental algorithm to construct a constrained
                 Delaunay triangulation of a set of points in the plane
                 (nodes). The triangulation covers the convex hull of
                 the nodes but may include polygonal constraint regions
                 whose triangles are distinguishable from those in the
                 remainder of the triangulation. This effectively allows
                 for a nonconvex or multiply connected triangulation
                 (the complement of the union of constraint regions)
                 while retaining the efficiency of searching and
                 updating a convex triangulation. The package provides a
                 wide range of capabilities including an efficient means
                 of updating the triangulation with nodal additions or
                 deletions. For N  nodes, the storage requirement is
                 13N integer storage locations in addition to the 2N 
                 nodal coordinates.


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Meanwhile I got also feedback from the original author, especially regarding 
the copyright situation:
##############################################################################
Albrecht,

I took a quick look at your addition of TRIPACK to R, and it
looks very nice.  I'm very pleased that you found my code useful.

There is an updated version of TRIPACK available from netlib and
described in Remark on Algorithm 751, ACM TOMS, Vol 25, No. 1,
March 1999, pp 97-98.  It adds some capabilities and correcta a
couple of possible bugs.  A LaTeX file is attached.

I cannot give you a definitive answer to the copyright question.
The question was still being debated when I was an ACM editor, and
I have not carefully read the current policy.  There may be a
requirement that the source code retain the ACM copyright notice
or something like that.  I suggest that you pose the question to
the current CALGO EIC, Tim Hopkins (t.r.hopkins@ukc.ac.uk).

Feel free to contact me if you encounter problems in the code.

Robert
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