%--------------------------------------------------------------------------
% function fitpara = gaussfit(x,d)
%
% d  distribution to be tested
% x  variable of distribution d
%
% returns:
%  fit to a gaussian distribution
%  para  [s,c,z] 
%   s sigma, 
%   c amplitude, 
%   z shift along x
%
%  2-May-2003 S. Schreiber
% 11-Jun-2004 S. Schreiber  add more sufficticated rms estimate if rms over
%                           whole profile gets negative
%--------------------------------------------------------------------------
function fitpara = gaussfit(x,d)

if isempty(x) | isempty(d)
    fitpara = [0,0,0];
    return
end
if size(x) ~= size(d) | size(x) < 4 
    fitpara = [0,0,0];
    return
end
% estimate of parameters:
bw = abs(x(2)-x(1));
dim=size(d);
%av = sum(d.*x)/sum(d);
%s = sum(d.*(x-av).^2)/sum(d);

%if s>0 | s>dim(2)/10;
%    s=sqrt(s);
%else
    fraction=5;
    mmax=find(d==max(d));
    lm=max(1,fix(mmax-dim(2)/fraction));
    rm=min(dim(2),fix(mmax+dim(2)/fraction));
    av=sum(d(lm:rm).*x(lm:rm))/sum(d(lm:rm));
    s=sum(d(lm:rm).*(x(lm:rm)-av).^2)/sum(d(lm:rm));
    if s>0
        s=sqrt(s);
    else
        s=sqrt(dim(2)/10.);
    end
    %end
c = sum(d)/bw;
if c<0
    dim=size(d);
    mmax=find(d==max(d));
    lm=max(1,fix(mmax-dim(2)/5));
    rm=min(dim(2),fix(mmax+dim(2)/5.));
    c = sum(d(lm:rm));
end
    
z = x(find(d==max(d)));

% do the fit by minimizing chi square

opts = optimset('TolX',1e-3,'MaxFunEvals',10000,'MaxIter',1000,'Display','off');
[fitpara,fval,flag,err] = fminsearch(@gausschisq,[s,c,z],opts,x,d);

if flag == 1
    disp(' Gauss fit converged.') 
    disp([' fitpara (inital)= ',num2str([s,c,z])])
    disp([' fitpara (final) = ',num2str(fitpara)])
    disp(['    fval = ',num2str(fval),' flag = ',num2str(flag)])
    disp(err)
else
    disp(' Gauss fit did not converge.') 
    disp([' fitpara (inital)= ',num2str([s,c,z])])
    disp([' fitpara (final) = ',num2str(fitpara)])
    disp(['    fval = ',num2str(fval),' flag = ',num2str(flag)])
    disp(err)
    
    fitpara = [0,0,0];

end


return