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: scstd.m
    path of file: ./repos/malini/Codes/FC_EC_calculation code/DynamicFC/jplv7/var_bvar
    
    the code of the file until where you have to start completion: function scale = scstd(y,nobs,nlag,xx)
% PURPOSE: determines bvar() function scaling factor using a
%          univariate AR model (called by bvar() only)
%---------------------------------------------------
% USAGE:   scale = scstd(y,nobs,nlag)
% where:    y    = an (nobs x neqs) matrix of y-vectors in levels
%           nlag = the lag length
%           nobs = # of observations in y
%---------------------------------------------------
% RETURNS:

    
function scale = scstd(y,nobs,nlag,xx)
% PURPOSE: determines bvar() function scaling factor using a
%          univariate AR model (called by bvar() only)
%---------------------------------------------------
% USAGE:   scale = scstd(y,nobs,nlag)
% where:    y    = an (nobs x neqs) matrix of y-vectors in levels
%           nlag = the lag length
%           nobs = # of observations in y
%---------------------------------------------------
% RETURNS:
%  scale = std deviation of the residuals 
%---------------------------------------------------

% written by:
% James P. LeSage, Dept of Economics
% University of Toledo
% 2801 W. Bancroft St,
% Toledo, OH 43606
% jpl@jpl.econ.utoledo.edu

if nargin == 3
    nx = 0;
elseif nargin == 4
    [junk,nx] = size(xx);
end