Dear Gabor, Thank you for your reply. In fact I am ajusting several models at same time, like linear, log-linear, log-log, piecewise etc. One of the models are the power model. I really need to fit a power model because it one of the hypothesis which have been suggested on literature.
In addition, there are other variables which are beeing tested as explanatory. Kind regards, miltinho ----- Mensagem original ---- De: Gabor Grothendieck <[EMAIL PROTECTED]> Para: Milton Cezar Ribeiro <[EMAIL PROTECTED]> Cc: R-help <[EMAIL PROTECTED]> Enviadas: Domingo, 2 de Dezembro de 2007 17:28:23 Assunto: Re: [R] fitting "power model" in nls() Is that really the model we want? When we have problems sometimes its just a sign that the model is not very good in the first place. plot(richness ~ area) shows most of the points crowded the left and just a few points out to the right. This does not seem like a very good pattern for model fitting. plot(richness ~ log(area)) plot(log(richness) ~ log(area)) both look nicer. On Dec 2, 2007 2:08 PM, Milton Cezar Ribeiro <[EMAIL PROTECTED]> wrote: > Dear all, > I am still fighting against my "power model". > I tryed several times to use nls() but I can´t run it. > I am sending my variables and also the model which I would like to fit. > As you can see, this "power model" is not the best model to be fit, but I > really need also to fit it. > > The model which I would like to fit is Richness = B*(Area^A) > > richness<-c(44,36,31,39,38,26,37,33,34,48,25,22,44,5,9,13,17,15,21,10,16,22,13,20,9,15,14,21,23,23,32,29,20, > 26,31,4,20,25,24,32,23,33,34,23,28,30,10,29,40,10,8,12,13,14,56,47,44,37,27,17,32,31,26,23,31,34, > 37,32,26,37,28,38,35,27,34,35,32,27,22,23,13,28,13,22,45,33,46,37,21,28,38,21,18,21,18,24,18,23,22, > 38,40,52,31,38,15,21) > area<-c(26.22,20.45,128.68,117.24,19.61,295.21,31.83,30.36,13.57,60.47,205.30,40.21, > 7.99,1.18,5.40,13.37,4.51,36.61,7.56,10.30,7.29,9.54,6.93,12.60, > 2.43,18.89,15.03,14.49,28.46,36.03,38.52,45.16,58.27,67.13,92.33,1.17, > 29.52,84.38,87.57,109.08,72.28,66.15,142.27,76.41,105.76,73.47,1.71,305.75, > 325.78,3.71,6.48,19.26,3.69,6.27,1689.67,95.23,13.47,8.60,96.00,436.97, > 472.78,441.01,467.24,1169.11,1309.10,1905.16,135.92,438.25,526.68,88.88,31.43,21.22, > 640.88,14.09,28.91,103.38,178.99,120.76,161.15,137.38,158.31,179.36,214.36,187.05, > 140.92,258.42,85.86,47.70,44.09,18.04,127.84,1694.32,34.27,75.19,54.39,79.88, > 63.84,82.24,88.23,202.66,148.93,641.76,20.45,145.31,27.52,30.70) > plot(richness~area) > > I tryed to fit the following model: > > m1<-nls(richness ~ Const+B*(area^A)) > > Thanks a lot, > miltinho > Brazil. > > > > para armazenamento! > > [[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. > > para armazenamento! [[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.