[R] bootstrap and nls

From: Patrick Giraudoux <patrick.giraudoux_at_univ-fcomte.fr>
Date: Sun 18 Jul 2004 - 17:13:23 EST


Hi,

I am trying to bootstrap the difference between each parameters among two non linear regression (distributed loss model) as following:

# data.frame
> Raies[1:10,]

   Tps SolA Solb

1    0 32.97 35.92
2    0 32.01 31.35
3    1 21.73 22.03
4    1 23.73 18.53
5    2 19.68 18.28
6    2 18.56 16.79
7    3 18.79 15.61
8    3 17.60 13.43
9    4 14.83 12.76
10   4 17.33 14.91

etc...

# non linear model (work well)

RaiesLossA.nls<-nls(SolA~a/(1+b*Tps)^c,start=c(a=32,b=0.5,c=0.6)) RaiesLossB.nls<-nls(Solb~a/(1+b*Tps)^c,start=c(a=33,b=1.5,c=0.5))

# bootstrap
library(boot)

dif.param<-function(data,i){
RaiesLossA.nls<-nls(SolA[i]~a/(1+b*Tps[i])^c,start=c(a=31,b=0.5,c=0.6))
RaiesLossB.nls<-nls(Solb[i]~a/(1+b*Tps[i])^c,start=c(a=33,b=1.4,c=0.5))
RaiesLossA.nls$m$getPars()-RaiesLossB.nls$m$getPars() }

> myboot<-boot(Raies,dif.param,R=1000)

Error in numericDeriv(form[[3]], names(ind), env) :

        Missing value or an Infinity produced when evaluating the model

It seems that the init values (start=) may come not to be suitable while bootstraping. Data can be sent offline to whom wanted to try on the dataset.

Any hint welcome!

Best regards,

Patrick Giraudoux

University of Franche-ComtÚ
Department of Environmental Biology
EA3184 af. INRA
F-25030 Besanšon Cedex

tel.: +33 381 665 745
fax.: +33 381 665 797
http://lbe.univ-fcomte.fr

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https://www.stat.math.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide! http://www.R-project.org/posting-guide.html Received on Sun Jul 18 17:22:41 2004

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