option nocenter ps=50 ls=72;

data one;
 input trt response @@;
 cards;
 1 20 1 23 1 22
 2 24 2 26 2 25
 3 26 3 27 3 27
;

data two;
 set one;
 if trt = 1 then x1=1;
 else x1=0;
 if trt = 2 then x2=1;
 else x2=0;

data three;
 set one;
 if trt = 1 then x1=1;
 else if trt = 3 then x1=-1;
 else x1=0;
 if trt = 2 then x2=1;
 else if trt = 3 then x2=-1;
 else x2=0;

proc glm data=one;
 class trt;
 model response=trt /solution xpx;
 
proc reg data=two;
 model response=x1 x2;

proc reg data=three;
 model response=x1 x2;
run;