You are an expert in writing code in many different languages. Your goal is to perform code completion for the following code, keeping in mind the rest of the code and the file meta data.
    Metadata details:
    filename: ssqi.m
    path of file: ./repos/fecgsyn/subfunctions/sqi-analysis/sqi_metrics
    
    the code of the file until where you have to start completion: function sqi = ssqi(signal)
%sSQI Skewness SQI
% 
% Returns the skewness of a signal
% 
% 
% Input:
%   signal:         single channel (F)ECG [1xN double]
% 
% Output:
%   sqi:            resulting sSQI for segment
% 
% Reference:
% [1] Li, Q., Mark, R. G., Clifford, G. D., & Li. (2008). Robust heart rate 
% estimation from multiple asynchronous noisy sources using signal quality 
% indices and a Kalman filter. Physiol. Meas., 29(1), 15–32. 
% http://doi.org/10.1088/0967-3334/29/1/002
% 
% --
% fecgsyn toolbox, version 1.2, March 2017
% Released under the GNU General Public License
%
% Copyright (C) 2017  Joachim Behar & Fernando Andreotti
% Department of Engineering Science, University of Oxford
% joachim.behar@oxfordalumni.org, fernando.andreotti@eng.ox.ac.uk
%
% 
% For more information visit: http://www.fecgsyn.com
% 
% Referencing this work
% (SQI indices)
% Andreotti, F., Gräßer, F., Malberg, H., & Zaunseder, S. (2017). Non-Invasive Fetal ECG Signal Quality Assessment for 
% Multichannel Heart Rate Estimation. IEEE Trans. Biomed. Eng., (in press).
%  
% (FECGSYN Toolbox)
% Behar, J., Andreotti, F., Zaunseder, S., Li, Q., Oster, J., & Clifford, G. D. (2014). An ECG Model for Simulating 
% Maternal-Foetal Activity Mixtures on Abdominal ECG Recordings. Physiol. Meas., 35(8), 1537–1550.
% 
%
% Last updated : 15-03-2017
% 
% 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 3 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

    
function sqi = ssqi(signal)
%sSQI Skewness SQI
% 
% Returns the skewness of a signal
% 
% 
% Input:
%   signal:         single channel (F)ECG [1xN double]
% 
% Output:
%   sqi:            resulting sSQI for segment
% 
% Reference:
% [1] Li, Q., Mark, R. G., Clifford, G. D., & Li. (2008). Robust heart rate 
% estimation from multiple asynchronous noisy sources using signal quality 
% indices and a Kalman filter. Physiol. Meas., 29(1), 15–32. 
% http://doi.org/10.1088/0967-3334/29/1/002
% 
% --
% fecgsyn toolbox, version 1.2, March 2017
% Released under the GNU General Public License
%
% Copyright (C) 2017  Joachim Behar & Fernando Andreotti
% Department of Engineering Science, University of Oxford
% joachim.behar@oxfordalumni.org, fernando.andreotti@eng.ox.ac.uk
%
% 
% For more information visit: http://www.fecgsyn.com
% 
% Referencing this work
% (SQI indices)
% Andreotti, F., Gräßer, F., Malberg, H., & Zaunseder, S. (2017). Non-Invasive Fetal ECG Signal Quality Assessment for 
% Multichannel Heart Rate Estimation. IEEE Trans. Biomed. Eng., (in press).
%  
% (FECGSYN Toolbox)
% Behar, J., Andreotti, F., Zaunseder, S., Li, Q., Oster, J., & Clifford, G. D. (2014). An ECG Model for Simulating 
% Maternal-Foetal Activity Mixtures on Abdominal ECG Recordings. Physiol. Meas., 35(8), 1537–1550.
% 
%
% Last updated : 15-03-2017
% 
% 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 3 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/>.



sqi=skewness(signal);

end