options ls=79 ps=50;

/* read data */
data dat;
   infile 'leprosy.dat' firstobs=2;
   input drug $ before after;

proc glm;			/* before and after by drug */
   class drug;
   model before after = drug;
   means drug;

proc glm data=dat;		/* parallel lines */
   class drug;
   model after = before drug;
   lsmeans drug / stderr pdiff;
   output out=lepfit p=pafter r=rafter;
proc plot;			/* scatter plot with lines */
   plot after*before=drug pafter*before='*' / overlay; 
   plot rafter*pafter=drug;	/* diagnostic plot of residuals */


proc glm data=dat;		/* partial plot adjusted for drug */
   class drug;
   model after = drug;
   output out=drug r=rafter;
proc glm;
   model rafter = before;
   output out=parta p=prafter;
proc plot data=parta;
   plot rafter*before=drug prafter*before='*' / overlay;

proc glm data=dat;		/* partial plot adjusted for before */
   class drug;
   model after = before;
   output out=before r=rafter p=pafter;
proc glm;
   class drug pafter;		
   model rafter = drug;
   output out=partb p=mrafter;
proc plot;
   plot rafter*pafter=drug mrafter*pafter='*' / overlay;

proc glm data=dat;		/* sequential tests */
   class drug;
   model after = drug before / ss1;
proc glm data=dat;
   class drug;
   model after = before drug / ss1;

proc glm data=dat;		/* adjusted tests */
   class drug;
   model after = before drug / ss3;

proc glm data=dat;		/* different slopes by factor */
   class drug;
   model after = before * drug;
   output out=lepifit p=pafter r=rafter;
proc plot;
   plot after*before=drug pafter*before='*';

proc glm data=lepfit;		/* check after parallel slope fit */
   class drug;
   model rafter = pafter * drug;
   output out=leprfit r=rrafter p=prafter;
proc plot;
   plot rafter*pafter=drug prafter*pafter='*' / overlay;