/* nllsqt2.sas  -- demonstration of nonlinear least squares */
/*   Gallant example                                        */
/*                                                          */
  options ls = 80 ;                  * easier to read output ;
  data a ;
    infile '~/www/aug00/chap9/gallant.dat' ;
    input @4 y x1 x2 x3 ;
 run ;
/*                                                          */
/*                    write out the data                    */
  proc print data=a ;
    title 'nllsqt2 -- nonlinear least squares problem' ;
    title2 'Gallant example -- default method is Gauss-Newton' ;
 run ;
/*                                                          */
/*                    nonlinear regression                  */
  proc nlin data=a ;
    model y = th1*x1 + th2*x2 + th4*exp(th3*x3) ; * model gives mean function ;
    der.th1 = x1 ;                     * derivatives wrto parameters ;
    der.th2 = x2 ;
    der.th3 = x3 * th4 * exp(th3*x3) ;
    der.th4 = exp(th3*x3) ;
    parameters th1 = -.05             /* initial values */
               th2 = 1.04
               th3 = -1.20
               th4 = -.53 ;
 run ;