[R-sig-ME] nonlinear mixed longitudinal model

[Lee, MinJae]

Hello,


I was trying to convert the Proc nlmixed SAS to nlme in R.

especially, I'm considering the approach of Thiébaut and *Gadda( *Mixed models for longitudinal left-censored repeated measures in SAS program:

proc nlmixed

parms alpha=1 beta1=1 beta2=1   s11=0.5 s22=0.5 se=1;
bounds 0<=s11, 0<s22, 0<se;
eta=alpha+beta1*&gp+beta2*day+ u1+day*u2;
ll=(1-&cens)*(log((1/(sqrt(2*(3.14159)*se)))*exp((-1/(2*se))*((&coags-eta)**2))))
+(&cens)*(log(probnorm((&coags-eta)/(sqrt(se)))));
model &coags ~ general(ll);

random u1 u2 ~ normal([0,0],[s11,0,s22]) subject=subjectid;



I know there are a lot of differences between them(nlmixed vs nlme), but I really need to convert this program to R.

could you please give any advise for me?

is there any appropriate packages in R for this model?



Thank you so much in advance,

Minjae Lee