/* nllsqt1.sas  -- demonstration of nonlinear least squares */
/*   Fuller example                                         */
/*                                                          */
  options ls = 80 ;                  * easier to read output ;
  data a ;
    infile '~/www/aug00/chap9/fulnls.dat' ;
    input y x ;
 run ;
/*                                                          */
/*                    write out the data                    */
  proc print data=a ;
    title 'nllsqt1 -- nonlinear least squares problem' ;
    title2 'Fuller example -- default method is Gauss-Newton' ;
 run ;
/*                                                          */
/*                    nonlinear regression                  */
  proc nlin data=a ;
    model y = th1 + th2*exp(-th3*x) ; * model gives mean function ;
    der.th1 = 1 ;                     * derivatives wrto parameters ;
    der.th2 = exp(-th3*x) ;
    der.th3 = -x * th2 * exp(-th3*x) ;
    parameters th1 = 140             /* initial values */
               th2 = -85
               th3 = 1.5 ;
 run ;