Message-ID: <20120515235435.M81422@oikos.unam.mx>
Date: 2012-05-16T00:08:44Z
From: Francisco Mora Ardila
Subject: confidence intervals for nls or nls2 model
Hi all
I have fitted a model usinf nls function to these data:
> x
[1] 1 0 0 4 3 5 12 10 12 100 100 100
> y
[1] 1.281055090 1.563609934 0.001570796 2.291579783 0.841891853
[6] 6.553951324 14.243274230 14.519899320 15.066473610 21.728809880
[11] 18.553054450 23.722637370
The model fitted is:
modellogis<-nls(y~SSlogis(x,a,b,c))
It runs OK. Then I calculate confidence intervals for the actual data using:
dataci<-predict(as.lm(modellogis), interval = "confidence")
BUt I don?t get smooth curves when plotting it, so I want to get other "confidence
vectors" based on a new x vector by defining a new data to do predictions:
x0 <- seq(0,15,1)
dataci<-predict(as.lm(modellogis), newdata=data.frame(x=x0), interval = "confidence")
BUt it does not work: I get the same initial confidence interval
Any ideas on how to get tconfidence and prediction intervals using new X data on a
previous model?
Thanks
Francisco
----------------------
Francisco Mora Ardila
Estudiante de Doctorado
Centro de Investigaciones en Ecosistemas
Universidad Nacional Aut?noma de M?xico