--- a/doc/ChangeLog	Mon Jul 02 20:19:38 2007 +0000
+++ b/doc/ChangeLog	Fri Jul 06 08:44:04 2007 +0000
@@ -1,3 +1,7 @@
+2007-07-06  David Bateman  <dbateman@free.fr>
+
+        * interpreter/arith.txi: Add accumarray.
+
 2007-06-25  John W. Eaton  <jwe@octave.org>
 
 	* interpreter/stats.txi: Reorganize sections and add introductory text.

--- a/doc/interpreter/arith.txi	Mon Jul 02 20:19:38 2007 +0000
+++ b/doc/interpreter/arith.txi	Fri Jul 06 08:44:04 2007 +0000
@@ -190,6 +190,8 @@
 
 @DOCSTRING(sumsq)
 
+@DOCSTRING(accumarray)
+
 @node Special Functions
 @section Special Functions
 

--- a/scripts/ChangeLog	Mon Jul 02 20:19:38 2007 +0000
+++ b/scripts/ChangeLog	Fri Jul 06 08:44:04 2007 +0000
@@ -1,3 +1,8 @@
+2007-07-06  David Bateman  <dbateman@free.fr>
+
+        * general/accumarray.m: New function to create an array by 
+        accumulating the elements.
+
 2007-06-29  Marcus W. Reble  <reble@wisc.edu>
 
 	* optimization/sqp.m (sqp): New args, lb, ub, maxiter, and tolerance.

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/scripts/general/accumarray.m	Fri Jul 06 08:44:04 2007 +0000
@@ -0,0 +1,134 @@
+## Copyright (C) 2007 David Bateman
+##
+## This program 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 of the License, or
+## (at your option) any later version.
+##
+## This program 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 this program; if not, write to the Free Software
+## Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
+## 02110-1301  USA
+
+## -*- texinfo -*-
+## @deftypefn {Function File} {} accumarray (@var{subs}, @var{vals}, @var{sz}, @var{fun}, @var{fillval}, @var{issparse})
+## @deftypefnx {Function File} {} accumarray (@var{csubs}, @var{vals}, @dots{})
+##
+## Creates an array by accumulating the elements of a vector into the
+## positions of defined by their subscripts. The subscripts are defined by
+## the rows of the matrix @var{subs} and the values by @var{vals}. Each row
+## of @var{subs} corresponds to one of the values in @var{vals}.
+##
+## The size of the matrix will be determined by the subscripts themselves.
+## However, if @var{sz} is defined it determines the matrix size. The length
+## of @var{sz} must correspond to the number of columns in @var{subs}.
+##
+## The default action of @code{accumarray} is to sum the elements with the
+## same subscripts. This behavior can be modified by defining the @var{fun}
+## function. This should be a function or function handle that accepts a 
+## column vector and returns a scalar. The result of the function should not
+## depend on the order of the subscripts.
+##
+## The elements of the returned array that have no subscripts assoicated with
+## them are set to zero. Defining @var{fillval} to some other value allows
+## these values to be defined.
+##
+## By default @code{accumarray} returns a full matrix. If @var{issparse} is
+## logically true, then a sparse matrix is returned instead.
+##
+## An example of the use of @code{accumarray} is:
+##
+## @example
+## @group
+## accumarray ([1,1,1;2,1,2;2,3,2;2,1,2;2,3,2],101:105)
+## @result{} ans(:,:,1) = [101, 0, 0; 0, 0, 0]
+##    ans(:,:,2) = [0, 0, 0; 206, 0, 208]
+## @end group
+## @end example
+## @end deftypefn
+
+function A = accumarray (subs, val, sz, fun, fillval, isspar)  
+
+  if (nargin < 2 || nargin > 6)
+    print_usage ();
+  endif
+
+  if (iscell(subs))
+    subs = cell2mat (cellfun (@(x) x(:), subs, 'UniformOutput', false));
+  endif
+  ndims = size (subs, 2);
+
+  if (nargin < 3 || isempty (sz))
+    sz = max (subs);
+    if (isscalar(sz))
+      sz = [sz, 1];
+    endif
+  else
+    if (length (sz) != ndims)
+      error ("accumarray: inconsistent dimensions");
+    endif
+  endif
+  
+  if (nargin < 4 || isempty (fun))
+    fun = @sum;
+  endif
+
+  if (nargin < 5 || isempty (fillval))
+    fillval = 0;
+  endif
+
+  if (nargin < 6 || isempty (isspar))
+    isspar = false;
+  endif
+  if (isspar)
+    if (ndims > 2)
+      error ("Can not have more than 2 dimensions in a sparse matrix");
+    endif
+  endif
+
+  [subs, idx] = sortrows (subs);
+  if (isscalar (val))
+    val = val * ones (size (idx));
+  else
+    val = val(idx);
+  endif
+  cidx = find([true; (sum (abs (diff (subs)), 2) != 0)]);
+  idx = cell (1, ndims);
+  for i = 1:ndims
+    idx{i} = subs (cidx, i);
+  endfor
+  x = cellfun (fun, mat2cell (val(:), diff ([cidx; length(val) + 1])));
+  if (isspar && fillval == 0)
+    A = sparse (idx{1}, idx{2}, x, sz(1), sz(2));
+  else
+    if (iscell (x))
+      ## Why did matlab choose to reverse the order of the elements
+      x = cellfun (@(x) flipud(x(:)), x, 'UniformOutput', false);
+      A = cell (sz);
+    elseif (fillval == 0)
+      A = zeros (sz, class(x));
+    else 
+      A = fillval .* ones (sz);
+    endif
+    A (sub2ind (sz, idx{:})) = x;
+  endif
+endfunction
+
+%!error (accumarray (1:5))
+%!error (accumarray ([1,2,3],1:2))
+%!assert (accumarray ([1;2;4;2;4],101:105), [101;206;0;208])
+%!assert (accumarray ([1,1,1;2,1,2;2,3,2;2,1,2;2,3,2],101:105),cat(3, [101,0,0;0,0,0],[0,0,0;206,0,208]))
+%!assert (accumarray ([1,1,1;2,1,2;2,3,2;2,1,2;2,3,2],101:105,[],@(x)sin(sum(x))),sin(cat(3, [101,0,0;0,0,0],[0,0,0;206,0,208])))
+%!assert (accumarray ({[1 3 3 2 3 1 2 2 3 3 1 2],[3 4 2 1 4 3 4 2 2 4 3 4],[1 1 2 2 1 1 2 1 1 1 2 2]},101:112),cat(3,[0,0,207,0;0,108,0,0;0,109,0,317],[0,0,111,0;104,0,0,219;0,103,0,0]))
+%!assert (accumarray ([1,1;2,1;2,3;2,1;2,3],101:105,[2,4],@max,NaN),[101,NaN,NaN,NaN;104,NaN,105,NaN])
+%!assert (accumarray ([1 1; 2 1; 2 3; 2 1; 2 3],101:105,[2 4],@prod,0,true),sparse([1,2,2],[1,1,3],[101,10608,10815],2,4))
+%!assert (accumarray ([1 1; 2 1; 2 3; 2 1; 2 3],1,[2,4]), [1,0,0,0;2,0,2,0])
+%!assert (accumarray ([1 1; 2 1; 2 3; 2 1; 2 3],101:105,[2,4],@(x)length(x)>1),[false,false,false,false;true,false,true,false])
+%!test
+%! A = accumarray ([1 1; 2 1; 2 3; 2 1; 2 3],101:105,[2,4],@(x){x});
+%! assert (A{2},[104;102])