* .
* NonLinear Regression.
MODEL PROGRAM  x00 = 1 x01 = 5.5 x02 = 9 x03 = 15.5 a1 = 1 a2 =1 a3 =1 a4 =1 b1 =1 b2 =1 b3 =1 b4 =1.


do if ((x <x01)  and (x > x00)).
compute pred_ = a1*exp(-b1*(x-x00)).

else if ((x <x02)  and (x > x01)).
compute pred_ = a2*exp(-b2*(x-x01)).

else if ((x <x03)  and (x > x02)).
compute pred_ = a3*exp(-b3*(x-x02)).

else  if (x > x03).
compute pred_ = a4*exp(-b4*(x-x03)).

end if.
CNLR y
  /OUTFILE='D:\george.sav'
  /PRED PRED_
/save pred_
  /BOUNDS x00 <= 1.06  ; x01 <=6.16; x02 <=10.59; x03 <=16.24
  /CRITERIA STEPLIMIT 2 ISTEP 1E+20 .

GRAPH
  /SCATTERPLOT(OVERLAY)=x x  WITH pred_ y (PAIR)
  /MISSING=LISTWISE .