/* Lesson 12-4 */
 /*    File Name = les1204.sas   07/05/07   */
options linesize=72 pagesize=20;

data air;
  infile 'usair2.prn';
  input id $ y x1 x2 x3 x4 x5 x6;
/*
  label y='SO2 of air in micrograms per cubic metre'
        x1='Average annual temperature in F'
        x2='Number of manufacturing enterprises employing 20 or more workers'
        x3='Population size (1970 census); in thousands'
        x4='Average annual wind speed in miles per hour'
        x5='Average annual precipitation in inches'
        x6='Average number of days with precipitation per year'
;
*/

proc print data=air(obs=10);
run;

proc corr data=air;
run;

proc reg data=air;
  model y=x1 x2 x3 x4 x5 x6;
  output out=outreg1 predicted=pred1 residual=resid1;
run;

proc plot data=outreg1;
  plot resid1*pred1  /vref=0;
  plot resid1*x1     /vref=0;
  plot resid1*x2     /vref=0;
  plot resid1*x3     /vref=0;
  plot resid1*x4     /vref=0;
  plot resid1*x5     /vref=0;
  plot resid1*x6     /vref=0;
  plot resid1*y      /vref=0;
run;

proc reg data=air;
  model y=x1-x6 / selection=stepwise;
  output out=outreg1 predicted=pred1 residual=resid1;
run;

proc print data=outreg1(obs=15);
run;

proc plot data=outreg1;
  plot resid1*pred1               /vref=0;
  plot resid1*(x1 x2 x3 x4 x5 x6) /vref=0;
  plot resid1*(x1-x6)             /vref=0;
  plot resid1*y                   /vref=0;
run;

proc reg data=air;
  model y=x1-x6 / selection=rsquare;
  output out=outreg1 predicted=pred1 residual=resid1;
run;