/* Analyze the data from a crossover 
   trial on cerebrovascular deficiency
   from example 8.1 in DHLZ   */

/*  THE VARIABLES WERE CODED AS FOLLOWS:                                                              
                                                                      
    ID = CLUSTER VARIABLE                                             
                                                                      
    CLASS = 1, NEEDED TO RUN GEE2                                     
                                                                      
    Y = 1  abnormal electrocardiogram
        0  normal electrocardiogram                                     
                                                                      
    Int = 1 (INTERCEPT)                                                
                                                                      
    X1 = 1 placebo (treatment B)
         0 active drug A                                     
                                                                      
    X2 = 1 if period 2 
         0 if period 1                              
                                                                      
    X12 = X1*X2                                                        
                                                                      
    order = 1 if B before A 
            0 if A before B       
                                                                                                                              
REFERENCE: JONES AND KENWARD(1989) 
              CHAPMAN AND HALL, P.9 */



data set1; 
  infile "c:\stat565\data\dhlz.example8_1.dat";
  input patient class y int x1 x2 x12 order ;
  /* Recode the variables */
  x1=abs(1-x1);
  x12=x1*x2;
  run;


/* First fit a model with an order effect */

proc genmod data=set1 descending;
  class patient;
  model y = x1 x2 x12 /
		   dist=binomial link=logit
		   itprint pscale
		   converge=1e-8 maxit=50;
  repeated subject=patient / type=un
                 modelse covb corrw;
  run;

  /* Fit a model ignoring any order effect */

proc genmod data=set1 descending;
  class patient;
  model y = x1 x2 /
		   dist=binomial link=logit
		   itprint pscale;
  repeated subject=patient / type=un
                 modelse covb corrw;
  run;


  /* Fit a model assuming completely
     independent responses  */

proc genmod data=set1 descending;
  class patient;
  model y = x1 x2 /
		   dist=binomial link=logit
		   itprint  robust
           aggregate=patient;
  run;