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+## Copyright (C) 1999,2000  Kai Habel
+##
+## This file is part of Octave.
+##
+## Octave is free software; you can redistribute it and/or modify it
+## under the terms of the GNU General Public License as published by
+## the Free Software Foundation; either version 2, or (at your option)
+## any later version.
+##
+## Octave is distributed in the hope that it will be useful, but
+## WITHOUT ANY WARRANTY; without even the implied warranty of
+## MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+## General Public License for more details.
+##
+## You should have received a copy of the GNU General Public License
+## along with Octave; see the file COPYING.  If not, write to the Free
+## Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
+## 02110-1301, USA.
+
+## -*- texinfo -*-
+## @deftypefn {Loadable Function} {@var{T} =} delaunay3 (@var{x}, @var{y}, @var{z})
+## @deftypefnx {Loadable Function} {@var{T} =} delaunay3 (@var{x}, @var{y}, @var{z}, @var{opt})
+## A matrix of size [n, 4] is returned. Each row contains a 
+## set of tetrahedron which are
+## described by the indices to the data point vectors (x,y,z).
+##
+## A fourth optional argument, which must be a string or cell array of strings,
+## contains extra options passed to the underlying qhull command.  See the 
+## documentation for the Qhull library for details.
+## @seealso{delaunay,delaunayn}
+## @end deftypefn
+
+## Author:	Kai Habel <kai.habel@gmx.de>
+
+function tetr = delaunay3 (x,y,z,opt)
+
+  if ((nargin != 3) && (nargin != 4))
+    print_usage ();
+  endif
+
+  if (isvector(x) && isvector(y) &&isvector(z) && ...
+      (length(x) == length(y)) && (length(x) == length(z)))
+    if (nargin == 3)
+      tetr = delaunayn([x(:),y(:),z(:)]);
+    elseif (ischar(opt) || iscell (opt))
+      tetr = delaunayn([x(:),y(:),z(:)], opt);
+    else
+      error("delaunay3: fourth argument must be a string or cell array of strings");
+    endif
+  else
+    error("delaunay3: first three input arguments must be vectors of same size");
+  endif
+
+endfunction
+
+%!test
+%! x = [-1, -1, 1, 0, -1]; y = [-1, 1, 1, 0, -1]; z = [0, 0, 0, 1, 1];
+%! assert (sortrows (sort (delaunay3 (x, y, z), 2)), [1,2,3,4;1,2,4,5])
+