options ls=80 nodate;
libname fu '../../sdata';
data work;
	set fu.myeloma;
	lbun = log(bun);
	hbsquare = hb*hb;
	if 7 < hb <= 10 then hb2 = 1; else hb2 = 0;
	if 10 < hb <= 13 then hb3 = 1; else hb3 = 0;
	if  hb > 13 then hb4 = 1; else hb4 = 0;
/* check non-linearity of HB */
proc phreg;
        model survt*censor(0)= lbun hb / rl;
proc phreg;
        model survt*censor(0)= lbun hb hbsquare / rl;

/* check non-linearity of HB: an alternative approach */
proc phreg;
        model survt*censor(0)= lbun hb2 hb3 hb4 / rl;
run;