function varargout = nls_resida(x,mode)
  
  global numf numg
  
  argout = 0;
  y = [0.14, 0.18, 0.22, 0.25, 0.29, 0.32, 0.35, 0.39, 0.37, ...
	0.58, 0.73, 0.96, 1.34, 2.10, 4.39]';
  i = [1:15]';
  vw = (16-i)*x(2) + min(i,16-i)*x(3);
  r = x(1)*ones(15,1) + i./vw - y;
  f = 0.5*sum(r.^2);
  if bitand(mode,1) 
    argout = argout + 1;
    numf = numf+1;
    varargout(argout) = {f};
  end
  if bitand(mode,2) 
    argout = argout + 1;
    J = [ones(15,1) -[i.*(16-i)./vw.^2] -[i.*min(i,16-i)./vw.^2]];
    numg=numg+1;
    varargout(argout) = {J'*r};
  end
  return;