function bhat=mafun(y,m);
% Usage: bhat=mafun(y,m);
% fitting a time sequence y into a MA(m) time series model
% bhat: a vector estimated MA coefficients [b(0) ... b(M-1)];
% call mfiles: autocorr.m
% (C) 2001 by Yu Hen Hu
% created: 10/28/2001

ry=autocorr(y,m);      % autocorrelation lags
sz=ry/max(ry);         % autocorrelation coefficients
rt=roots(sz);          % rt: a column vector
idx=find(abs(rt)<1);   % roots inside unit circle
idx1=find(abs(rt)==1); % roots on unit circle will be duplicates
if isempty(idx1),      % if no roots on unit circle
   broot=rt(idx);
else                   % if there is root on the unit circle, eliminte duplicates
   broot=[rt(idx) unique(rt(idx1))];
end
bhat=poly(broot);      % estimated polynomial