options nodate nonumber ps=55 ls=80;

data boston;
infile 'boston.dat';  /* You may need to specify a full
                         directory path to this file. */
input CRIM NOX AGE DIS PTRATIO LSTAT MEDV;
sample=ranuni(seed);
run;

proc sort;
by sample;
run;

data boston;
set boston;
if _n_ <= 30;
run;



proc reg;
model MEDV = CRIM NOX AGE DIS PTRATIO LSTAT /
  selection=rsquare cp adjrsq;
run;


proc reg;
model MEDV = CRIM NOX AGE DIS PTRATIO LSTAT /
  selection=stepwise sle=.25 sls=.10;
run;


proc reg;
model MEDV = CRIM NOX AGE DIS PTRATIO LSTAT /
  selection=forward sle=.25;
run;


proc reg;
model MEDV = CRIM NOX AGE DIS PTRATIO LSTAT /
  selection=backward sls=.10;
run;