You can use the CATMOD procedure interactively. After specifying a model with a MODEL statement and running PROC CATMOD with a RUN statement, you can execute any statement without reinvoking PROC CATMOD. You can execute the statements singly or in groups by following the single statement or group of statements with a RUN statement. Note that you can use more than one MODEL statement; this is an important difference from the GLM procedure.

If you use PROC CATMOD interactively, you can end the CATMOD procedure with a DATA step, another PROC step, an ENDSAS statement, or a QUIT statement. The syntax of the QUIT statement is as follows:

   quit;

When you are using PROC CATMOD interactively, additional RUN statements do not end the procedure run but tell the procedure to execute additional statements.

When the CATMOD procedure detects a BY statement, it disables interactive processing; that is, once the BY statement and the next RUN statement are encountered, processing proceeds for each BY group in the data set, and no additional statements are accepted by the procedure. For example, the following statements perform three analyses: one for the entire data set, one for males, and one for females:

   proc catmod;
      weight wt;
      response marginals;
      model r1*r2=a|b;
   run;
      by sex;
   run;

Note that the BY statement can appear after the first RUN statement; this is an important difference from PROC GLM, which requires that the BY statement appear before the first RUN statement.