The model is not identifiable since if (a, b, g) is a solution then so is every multiple of it.
On 9/30/07, Irene Mantzouni <[EMAIL PROTECTED]> wrote: > Dear all, > > I would like to fit a non-linear model of the form: > y=g*x/(a+b*x) > with nls(). > However this model is somehow overparameterized and I get the error message > about > singular gradient matrix at initial parameter estimates. > What I am interested in is to make inference about parameters b and g, so > this has to be taken into account in the model formulation. > What options do I have? > Also, how is it possible to fit a partially linear model? > > Thank you!! > > Irene Mantzouni > ---------------- > PhD student > DIFRES > > ______________________________________________ > R-help@r-project.org mailing list > https://stat.ethz.ch/mailman/listinfo/r-help > PLEASE do read the posting guide http://www.R-project.org/posting-guide.html > and provide commented, minimal, self-contained, reproducible code. > ______________________________________________ R-help@r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code.
