Hi > > Dear list, > > I'm trying to fit a chapman-richards equation to my data, only I > cannot interpret the parameters a, b and d. I know that the parameter > b denotes the asymptote, but for the others I couldn't figure out. But
No. d Is asymptote. You can easily check how the function behives by fff<- function(x, a=1,b=1,d=1) d*(1-exp(-b *x))^a and changing the values of a,b,d, plot(1:100, fff(1:100, a=..., b=..., d=...) e.g. plot(1:100, fff(1:100, a=1000, b=1,d=10)) points(1:100, fff(1:100, a=1000, b=.1,d=10), col=2) Regards Petr > I do need to know this in order to set my starting values. Here's the > model: > > modPoplar<- nls(Diameter ~ d*(1-exp(-b *Age))^a ,start=list(a=20,b=0.9,d=33)) > > I attached the graph, too. > > Hoping for your answers! > > Best, Anna > > -- > > > > Der Inhalt dieser E-Mail ist vertraulich. Sollte Ihnen die E-Mail > irrtümlich zugesandt worden sein, bitte ich Sie, mich unverzüglich zu > benachrichtigen und die E-Mail zu löschen. > > This e-mail is confidential. If you have received it in error, please > notify me immediately and delete it from your system. > > ______________________________________________ > 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.