Mike, Without completely knowing your end game with these questions and this procedure it does seem like you are "re-inventing the wheel" here. If that is true and given the nls() fit that you are using I would suggest that you look at boot.case() in the alr3 package or nlsBoot() in the nlstools package. I have used both of those functions with success when fitting the von Bertalanffy growth model to fish length-age data.
Some general help for fitting von Bertalanffy growth models to fish data can be found at http://www.ncfaculty.net/dogle/fishR/gnrlex/gnrlex.html > -----Original Message----- > From: r-help-boun...@r-project.org [mailto:r-help-boun...@r- > project.org] On Behalf Of Michael Larkin > Sent: Wednesday, September 29, 2010 2:57 PM > To: r-help@r-project.org > Subject: [R] fitting model to resampled data > > I apologize if this comes across as confusing. I will try to explain > my > situation as best I can. > > > > I have R bootstrapping my growth data for fish. It's resampling my > database > of age and length data and then produces several new datasets for me. > In > this case, it's resampling my data to create three new datasets of age > and > length data. Here is my code with my original data called growth: > > > > replicate(3, growth[sample(9,12,replace=T),], simplify = FALSE) > > > > This is working very well. > > > > Now, the problem that I am now stuck with is incorporating a growth > model > into the three new datasets to estimate growth parameters. Since there > are > now three new datasets I want to get three new estimates of the growth > parameters, essentially one from each new dataset. > > > > I am using the von Bertalanffy growth model. Here is my code: > > > > par<-list(Linf=700, K=0.20, to=-0.1) > #these are the starting values for parameters > > vb<-nls(Length~Linf*(1-exp(-K*(Age-to))), start=par, data=???) > #this is > the growth model with the parameters estimated with non linear least > > squares (nls) > > > > I tried placing my resampling function the data part of the nls > function but > it asks me for parameter estimates. > > > > Any advice would be greatly appreciated. > > > > Mike > > > > > [[alternative HTML version deleted]] > > ______________________________________________ > R-help@r-project.org mailing list > https://stat.ethz.ch/mailman/listinfo/r-help > PLEASE do read the posting guide http://www.R-project.org/posting- > guide.html > and provide commented, minimal, self-contained, reproducible code. ______________________________________________ R-help@r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code.
