options ls = 80 nodate;
libname fu '../../sdata';
data work;
	set fu.kidney; 
if neph = 1; /* patients on whom a  nephrectomy  has beeen performed*/ 
	if age = 1 then A1 = 1; else A1 = 0;
	if age = 3 then A3 = 1; else A3 = 0;
proc phreg;
        model survt*censor(0)= A1 A3 / covb rl;
run;