% NAN_STD - std, not considering NaN values
%
% Usage: std across the first dimension

% Author: Arnaud Delorme, CNL / Salk Institute, Sept 2003

% Copyright (C) 2003 Arnaud Delorme, Salk Institute, arno@salk.edu
%
% This file is part of EEGLAB, see http://www.eeglab.org
% for the documentation and details.
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%
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function out = nan_std(in)
    
    if nargin < 1
      help nan_std;
      return;
    end
    
    nans = find(isnan(in));
    in(nans) = 0;
   
    nonnans = ones(size(in));
    nonnans(nans) = 0;
    nonnans = sum(nonnans);
    nononnans = find(nonnans==0);
    nonnans(nononnans) = NaN;
   
    out = sqrt((sum(in.^2)-sum(in).^2./nonnans)./(nonnans-1));
    out(nononnans) = NaN;