%include data(fitnessd);
title 'Collinearity diagnostics';
options ls=90;

proc reg data=fitness;
	model oxy = age weight runtime rstpulse runpulse maxpulse /
			vif collinoint;
			
proc princomp data=fitness out=prin;
	var age weight runtime rstpulse runpulse maxpulse;
	run;

*-- Drop last component (biased, but no collinearity);
proc reg data=prin;
	model oxy = prin1-prin5 / vif;
	title2 'Incomplete PCA regression: drop last PC';
	run;

*-- redefine pulse rate variables;
data fit2;
	set fitness;
	pulse = (runpulse + maxpulse);
	pdiff = (maxpulse - runpulse);
	title2 'Redefine variables';
run;
proc reg data=fit2;
	model oxy = age weight runtime rstpulse pulse pdiff/ vif;
run;