For nls, the fixing (or masking) of parameters is not, to my knowledge, possible.
This is something I've been trying to get in such routines for over 2 decades. Masks are available, but not yet well documented, in Rcgmin and Rvmmin packages. However, these use an optim() style approach, which is quite different from nls(). If there's sufficient interest and some collaboration, I'd be willing to have a go at providing such functionality, but it would take quite a bit of work to provide the full capability of nls(). JN ______________________________________________ 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.
