--- a/scripts/set/setdiff.m
+++ b/scripts/set/setdiff.m
@@ -1,4 +1,5 @@
 ## Copyright (C) 2000, 2005, 2006, 2007 Paul Kienzle
+## Copyright (C) 2008 Jaroslav Hajek
 ##
 ## This file is part of Octave.
 ##
@@ -19,19 +20,22 @@
 ## -*- texinfo -*-
 ## @deftypefn {Function File} {} setdiff (@var{a}, @var{b})
 ## @deftypefnx {Function File} {} setdiff (@var{a}, @var{b}, "rows")
+## @deftypefnx {Function File} {[@var{c}, @var{i}] = } setdiff (@var{a}, @var{b})
 ## Return the elements in @var{a} that are 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.
 ##
 ## Given the optional third argument @samp{"rows"}, return the rows in
 ## @var{a} that are not in @var{b}, sorted in ascending order by rows.
+##
+## If requested, return @var{i} such that @code{c = a(i)}.
 ## @seealso{unique, union, intersect, setxor, ismember}
 ## @end deftypefn
 
 ## Author: Paul Kienzle
 ## Adapted-by: jwe
 
-function c = setdiff (a, b, byrows_arg)
+function [c, i] = setdiff (a, b, byrows_arg)
 
   if (nargin < 2 || nargin > 3)
     print_usage ();
@@ -50,7 +54,11 @@
   endif
 
   if (byrows)
-    c = unique (a, "rows");
+    if (nargout > 1)
+      [c, i] = unique (a, "rows");
+    else
+      c = unique (a, "rows");
+    endif
     if (! isempty (c) && ! isempty (b))
       ## Form a and b into combined set.
       b = unique (b, "rows");
@@ -58,9 +66,16 @@
       ## Eliminate those elements of a that are the same as in b.
       dups = find (all (dummy(1:end-1,:) == dummy(2:end,:), 2));
       c(idx(dups),:) = [];
+      if (nargout > 1)
+	i(idx(dups),:) = [];
+      endif
     endif
   else
-    c = unique (a);
+    if (nargout > 1)
+      [c, i] = unique (a);
+    else
+      c = unique (a);
+    endif
     if (! isempty (c) && ! isempty (b))
       ## Form a and b into combined set.
       b = unique (b);
@@ -72,6 +87,9 @@
 	dups = find (dummy(1:end-1) == dummy(2:end));
       endif
       c(idx(dups)) = [];
+      if (nargout > 1)
+	i(idx(dups)) = [];
+      endif
       ## Reshape if necessary.
       if (size (c, 1) != 1 && size (b, 1) == 1)
 	c = c.';
@@ -88,3 +106,9 @@
 %!assert(setdiff([1; 2; 3; 4], [1; 2; 4], "rows"), 3)
 %!assert(setdiff([1, 2; 3, 4], [1, 2; 3, 6], "rows"), [3, 4])
 %!assert(setdiff({"one","two";"three","four"},{"one","two";"three","six"}), {"four"})
+
+%!test
+%! a = [3, 1, 4, 1, 5]; b = [1, 2, 3, 4];
+%! [y, i] = setdiff (a, b.');
+%! assert(y, [5]);
+%! assert(y, a(i));