/*  fit the HCV data using the nlinmix macro  */

options ps=59 ls=80 nodate; run;

data hcv;  infile "hcvmix.dat";
  input id days vl;
run;

/*  use the results from nlme and nlinmix to get starting values */

proc nlmixed data=hcv;
     parms beta1=1.5 beta2=1.25 beta3=-0.16 s2b1=0.04 cb12 -0.005 s2b2=0.015
          cb13=-0.0008 cb23=0.001 s2b3=0.0004 sig=0.1 theta=1.0;
     v0=exp(beta1+b1);
     cc=exp(beta2+b2);
     e=exp(beta3+b3);
     t0=0.2; 
     dd=0;
     if days>t0 then dd=1;
     tt = dd*(days-t0);
     pred = v0*(1-e+e*exp(-cc*tt));
     var  = (sig**2)*(pred**(2*theta));
     model vl ~ normal(pred,var);
     random b1 b2 b3 ~ normal([0,0,0],[s2b1,cb12,s2b2,cb13,cb23,s2b3]) 
            subject=id;
run;