--- /dev/null
+## 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, see <http://www.gnu.org/licenses/>.
+
+## -*- texinfo -*-
+## @deftypefn {Function File} @var{m}= mean2 (@var{I})
+## Returns the mean value for a 2d real type matrix.
+## Uses @code{mean(I(:))}
+## @seealso{std2,mean}
+## @end deftypefn
+
+
+## Author: Kai Habel <kai.habel@gmx.de>
+## Date: 01/08/2000
+
+function m = mean2 (I)
+
+ if !(nargin == 1)
+ print_usage();
+ endif
+
+ if !(ismatrix(I) && isreal(I))
+ error("mean2: argument must be a real type matrix");
+ endif
+
+ m = mean (I(:));
+endfunction