[R-sig-ME] Model with variable number of arguments

[Daniel Kaschek]

Dear all,

I have the following model:

y_ij = x_i/s_j + (eps_ij)/s_j

where y_ij are the responses, x_i and s_j are the fixed effects and the
random effects follow a normal distribution

eps_ij ~ N(0, sigma0^2 + x_i^2 * sigmaR^2)

with error parameters sigma0 and sigmaR. In the end, I am interested in
the parameters x_i, s_j, sigma0 and sigmaR.

First of all, is lme4 the right package to solve this problem? When
looking at nlmer(), I had problems to figure out what would be the
correct structure of the function in the middle of the 3-part-formula.

Any help is appreciated.

Thanks a lot in advance,
Daniel