Specify nonlinear equation with nlme

justin bem <justin_bem <at> yahoo.fr> writes:

I want to estimate a nonlinear mixed effect model using nlme package or lme4.

How can I specify this

y=exp(B'X)/(1+exp(B'X)). the same model can be obtained with logit(y)=B'X but

I have many value of 1 in y logit(1)=Inf.

Using exp in this case is a fairly common approach, and there are some examples
in the Pinheiro/Bates Book, chapter 8.2 (look for orange tree); or, if you do
not have access to it, look at ch08.r in library/nlme/scripts

Dieter