[R] Interpreting parameters of sigmoid fct

[Anna Lee]

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
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.