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+## Copyright (C) 1995-2012 Kurt Hornik
+## Copyright (C) 2009 Jaroslav Hajek
+##
+## This file is part of Octave.
+##
+## Octave 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 3 of the License, or (at
+## your option) any later version.
+##
+## Octave 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 Octave; see the file COPYING.  If not, see
+## <http://www.gnu.org/licenses/>.
+
+## -*- texinfo -*-
+## @deftypefn  {Function File} {} meansq (@var{x})
+## @deftypefnx {Function File} {} meansq (@var{x}, @var{dim})
+## Compute the mean square of the elements of the vector @var{x}.
+## @tex
+## $$
+## {\rm meansq} (x) = {\sum_{i=1}^N {x_i}^2 \over N}
+## $$
+## where $\bar{x}$ is the mean value of $x$.
+## @end tex
+## @ifnottex
+##
+## @example
+## @group
+## std (x) = 1/N SUM_i x(i)^2
+## @end group
+## @end example
+##
+## @end ifnottex
+## For matrix arguments, return a row vector containing the mean square
+## of each column.
+##
+## If the optional argument @var{dim} is given, operate along this dimension.
+## @seealso{var, std, moment}
+## @end deftypefn
+
+## Author: KH <Kurt.Hornik@wu-wien.ac.at>
+## Description: Compute mean square
+
+function y = meansq (x, dim)
+
+  if (nargin != 1 && nargin != 2)
+    print_usage ();
+  endif
+
+  if (! (isnumeric (x) || islogical (x)))
+    error ("mean: X must be a numeric vector or matrix");
+  endif
+
+  nd = ndims (x);
+  sz = size (x);
+  if (nargin < 2)
+    ## Find the first non-singleton dimension.
+    (dim = find (sz > 1, 1)) || (dim = 1);
+  else
+    if (!(isscalar (dim) && dim == fix (dim))
+        || !(1 <= dim && dim <= nd))
+      error ("mean: DIM must be an integer and a valid dimension");
+    endif
+  endif
+
+  y = sumsq (x, dim) / sz(dim);
+
+endfunction
+
+
+%!assert(meansq (1:5), 11);
+%!assert(meansq (single(1:5)), single(11));
+%!assert(meansq (magic (4)), [94.5, 92.5, 92.5, 94.5]);
+%!assert(meansq (magic (4), 2), [109.5; 77.5; 77.5; 109.5]);
+
+%% Test input validation
+%!error meansq ()
+%!error meansq (1, 2, 3)
+%!error meansq (['A'; 'B']);
+%!error meansq (1, ones(2,2))
+%!error meansq (1, 1.5)
+%!error meansq (1, 0)
+%!error meansq (1, 3)
+