options ls = 78 nodate;
libname fu '../../sdata';
data w;
        set fu.ovarian;
/* Age alone */
proc nlmixed data = w;
parms lambda = 0.00002 theta = 0.0016 beta1 = 0; 
	xb = beta1 * age; 
	phi = exp(xb);
	St = exp((lambda * phi / theta)*(1 - exp(theta * survt)));
	ft = lambda * phi * exp(theta * survt) * St;
	ll = (cens = 1) * log(ft) + (cens = 0) * log(St);
        model ll ~ general(ll);
/* age and treatment (treat) */
proc nlmixed data = w;
parms lambda = 0.00002 theta = 0.0016 beta1 = 0 beta2 = 0.3; 
	xb = beta1 * age + beta2 * treat; 
	phi = exp(xb);
	St = exp((lambda * phi / theta)*(1 - exp(theta * survt)));
	ft = lambda * phi * exp(theta * survt) * St;
	ll = (cens = 1) * log(ft) + (cens = 0) * log(St);
        model ll ~ general(ll);
run;