problem with nls starting values
On Thu, Sep 27, 2012 at 12:43 PM, Benedikt Gehr
<benedikt.gehr at ieu.uzh.ch> wrote:
now I feel very silly! I swear I was trying this for a long time and it didn't work. Now that I closed R and restarted it it works also on my machine. So is the only problem that my model is overparametrized with the data I have?
Probably.
however shouldn't it be possible to fit an nls to these data?
(Obviously) no. I suggest you do a little reading up on optimization. Over-parameterization creates high dimensional ridges. -- Bert
thanks for the help Am 27.09.2012 21:27, schrieb Berend Hasselman:
y_val<-115-118*exp(-0.12*(seq(1,100)+rnorm(100,0,0.8)))
x_val<-seq(1:100) plot(y_val~x_val)
summary(mod1<-nls(y_val~a-b*exp(-c*x_val),start=list(a=115,b=118,c=0.12)))
-- Benedikt Gehr Ph.D. Student Institute of Evolutionary Biology and Environmental Studies University of Zurich Winterthurerstrasse 190 CH-8057 Zurich Office 13 J 36b Phone: +41 (0)44 635 49 72 http://www.ieu.uzh.ch/staff/phd/gehr.html
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