Message-ID: <1236339201.49b10a0175117@webmail.uu.se>
Date: 2009-03-06T11:33:21Z
From: Swantje Löbel
Subject: fitting a gompertz model through the origin using nls
Dear all!
I tried to fit Gompertz growth models to describe cummulative germination rates
using nls. I used the following code:
germ.model<-nls(percent.germ~a*exp(-b*exp(-k*day)),data=tab,start=list(a=100,b=10,k=0.5))
My problem is that I want that the fitted model goes through the origin, since
germination cannot start before the experiment was started, and y-max should be
100.
Does anyone know how I can achieve this?
Thanks a lot in advance! Swantje