* Log-linear model with interaction for clam data;
 options linesize=70;

 data clam;
 input species $ modif y @@;
 cards;
 s 0  3  s 1  0
 h 0 20  h 1  1

 proc genmod;
 class species modif;
 model y = species modif species*modif / dist=poisson
                                         link=log
                                         type1;
 run;