libname jason "/home/jaosborn/classes/st512sum08/datafiles";
data cars;
   set jason.cars1993;
   weight2=weight*weight;
run;


data grid;
   do weight=1500 to 4200 by 100;  
   do wheelbase=90 to 120;
      citympg=.;  weight2=weight*weight;
      output;
   end;
   end;
run;
data both;
   set grid cars; 
   wheelw = wheelbase*weight;
   wheelww= wheelbase*weight2;
run;
proc reg data=both;
   title "overfit, but pretty to look at";
   model citympg=weight weight2 wheelbase wheelw wheelww;
   output out=forgrid p=p;
run;
proc g3d data=forgrid;
   scatter weight*wheelbase=p;
run;

proc reg data=both;
   title "more parsimonious model";
   model citympg=weight weight2 wheelbase; 
   output out=forgrid2 p=p;
run;
proc g3d data=forgrid2;
   scatter weight*wheelbase=p;
run;