option nocenter ps=65 ls=80;

data lambs;
 input diet wtgain;
 cards;
  1  8 
  1 16
  1  9
  2  9
  2 16
  2 21
  2 11
  2 18
  3 15
  3 10
  3 17
  3  6
;

symbol1 bwidth=5 i=box;
axis1 offset=(5);
proc gplot;
 plot wtgain*diet / frame haxis=axis1;
run;

proc glm;
 class diet;
 model wtgain=diet;
 output out=diag r=res p=pred;
run;

proc gplot;
 plot res*diet /frame haxis=axis1;
run;

proc sort; by pred;
symbol1 v=circle i=sm50;
proc gplot;
 plot res*pred / haxis=axis1;
run;