* NonLinear Regression.
MODEL PROGRAM B0=10 B1=.05  b2 =-.001.
COMPUTE x0 = -b1/(2*b2).
do if (density < x0).
 COMPUTE PRED_ = b0 + b1*density+b2*density*density.
ELSE. 
COMPUTE PRED_ = b0 + b1*x0+b2*x0*x0.
END IF.
NLR eaten
  /OUTFILE='D:\mspeed\LOCALS~1\Temp\spss3304\SPSSFNLR.TMP'
  /PRED PRED_
  /SAVE PRED 
  /CRITERIA SSCONVERGENCE 1E-8 PCON 1E-8 .