DATA  ONE; INFILE 'c:\mixdemo\schizx1.dat' ;
INPUT ID imps79 imps79b imps79o int tx week sweek txswk;

/* get rid of observations with missing values */
if imps79 > -9;

/* get rid of weeks with very few observations */
IF week EQ 0 OR week EQ 1 OR week EQ 3 OR week EQ 6;

PROC FORMAT;
     VALUE imps79b 0 = 'le mild' 1 = 'ge moderate';
     VALUE tx      0 = 'placebo' 1 = 'drug';

/* gee logistic regression model: unstructured */
PROC GENMOD DESCENDING;
  CLASS id week;
  MODEL  imps79b = tx sweek txswk / LINK=LOGIT DIST=BIN;
  REPEATED SUBJECT=id / WITHIN=week CORRW TYPE=UN;
RUN;