options nocenter ls=75;

data impurity;
input trt blk y @@;
cards;
1 1 5 1 2 3 1 3 1 2 1 4 2 2 1 2 3 1
3 1 6 3 2 4 3 3 3 4 1 3 4 2 2 4 3 1 
5 1 5 5 2 3 5 3 2 
;

proc glm;
class blk trt;
model y = blk trt;
output out=resid1 r=res1 p=pred1;

data resid1;
 set resid1;
 predsq1 = pred1*pred1;

proc glm;
 class blk trt;
 model predsq1 = blk trt;
 output out=resid r=res2 p=pred2;
 
proc glm;
 model res1=res2;