Hi! I would suggest trying out a few different starting values as a first unsystematic approach.
For example changing hill=1 to hill=2 results in convergence: foo.nls<-nls(var~Emax*(Dose^hill)/((EC50^hill)+(Dose^hill)), start=list(Emax=-4,EC50=269,hill=2),trace=T,data=foo) Christian ______________________________________________ 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.
