/* Adapted from code provide by Dale McLerran of */
/* Fred Hutchinson Cancer Research Center */
data test;
/* We set a seed here; trying to use the default seed=0 within the */
/* DO loop doesn't work well                                       */
seed=12345679;
/* Generate a ZIP sample with a mixing proportion */
/* p0 of .5 and a Poisson mean lambda of 2 */
p0=.5;
do i=1 to 100;
/* Generate the Bernoulli mixing random variable */
  call ranbin(seed,1,p0,zero_inflate);
  lambda=2;
/* Generate the response */
  if zero_inflate then y=0;
  else call ranpoi(seed,lambda,y);
  output;
end;
keep y lambda;
run;
/* Fit the model in NLMIXED.  Use the same start */
/* values as in the algorithm that created the file */

proc nlmixed data=test;
parms p0=.5 mu0=2;
if y=0 then prob=p0+(1-p0)*exp(-mu0);
if y=0 then loglike=log(prob);
else loglike=log(1-p0)+y*log(mu0)-mu0-lgamma(y+1);
model y~general(loglike);
run;