data data_prg.reg6_6a;
set data_prg.reg6_6;
x11=x1*x1;x22=x2*x2;x33=x3*x3;
run;
proc reg data=data_prg.reg6_6a;
model y=x1-x3 x11 x22 x33/selection=stepwise ; 
model y=x1-x3 x11 x22 x33/selection=b noint; 
model y=x1-x3 x11 x22 x33/selection=f noint; 
model y=x2 x22 x33/selection=stepwise noint r cli influence  collin ; 
run; 
quit;