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+## Copyright (C) 2000 Paul Kienzle
+##
+## 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., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
+
+## -*- texinfo -*-
+## @deftypefn {Function File} {} setdiff(@var{a}, @var{b})
+##
+## Return the elements in @var{a} but not in @var{b}, sorted in ascending
+## order. If @var{a} and @var{b} are both column vectors return a column
+## vector, otherwise return a row vector.
+##
+## @end deftypefn
+## @seealso{unique, union, intersect, setxor, ismember}
+
+function c = setdiff(a,b)
+  if nargin != 2
+    usage("setdiff(a,b)");
+  endif
+
+  c = unique(a);
+  if !isempty(c) && !isempty(b)
+    ## form a and b into combined set
+    b = unique(b);
+    [dummy, idx] = sort([ c(:) ; b(:)]);
+    ## eliminate those elements of a that are the same as in b
+    n = length(dummy);
+    c(idx(find(dummy(1:n-1) == dummy(2:n)))) = [];
+    ## reshape if necessary
+    if ( size(c,1) != 1 && size(b,1) == 1 )
+      c = c.';
+    endif
+  endif
+endfunction
+  
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