```
function [SE,M]=sem(x,DIM)
% SEM calculates the standard error of the mean
%
% [SE,M] = SEM(x [, DIM])
% calculates the standard error (SE) in dimension DIM
% the default DIM is the first non-single dimension
% M returns the mean.
% Can deal with complex data, too.
%
% DIM dimension
% 1: SEM of columns
% 2: SEM of rows
% N: SEM of N-th dimension
% default or []: first DIMENSION, with more than 1 element
%
% features:
% - can deal with NaN's (missing values)
% - dimension argument
% - compatible to Matlab and Octave
%
% see also: SUMSKIPNAN, MEAN, VAR, STD
% 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/>.
% Copyright (C) 2000-2003 by Alois Schloegl <a.schloegl@ieee.org>
% $Revision: 4585 $
% $Id: sem.m 4585 2008-02-04 13:47:45Z adb014 $
if nargin>1,
[S,N,SSQ] = sumskipnan(x,DIM);
else
[S,N,SSQ] = sumskipnan(x);
end
M = S./N;
SE = (SSQ.*N - real(S).^2 - imag(S).^2)./(N.*N.*(N-1));
SE(SE<=0) = 0; % prevent negative value caused by round-off error
SE = sqrt(real(SE));
```

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