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+## Copyright (C) 2000  Kai Habel
+##
+## 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} @var{m}= mean2 (@var{I})
+## returns the mean value for a 2d real type matrix.
+## Uses @code{mean(I(:))}
+## @end deftypefn
+## @seealso{std2,mean}
+
+
+## Author:	Kai Habel <kai.habel@gmx.de>
+## Date:	01/08/2000
+
+function m = mean2 (I)
+
+  if !(nargin == 1)
+    usage ("mean2(I)");
+  endif
+
+  if !(is_matrix(I) && isreal(I))
+	error("argument must be a real type matrix");
+  endif
+
+  m = mean (I(:));
+endfunction