I would suggest to try different starting values. The following works for instance: n2<-nls(proc~f(cls,a,b,c,d),data=bline,start=list(a=1000,b=-1,c=4,d=1),t race=TRUE)
-----Original Message----- From: r-help-boun...@r-project.org [mailto:r-help-boun...@r-project.org] On Behalf Of Jorge I Velez Sent: Mittwoch, 10. April 2013 13:35 To: catalin roibu Cc: R mailing list Subject: Re: [R] non linear equation Please do not forget to CC the list to increase your chances of getting help. --JIV On Wed, Apr 10, 2013 at 9:31 PM, catalin roibu <catalinro...@gmail.com>wrote: > Hello! > I try to compute the double exponential function this code: > f<-function(cls,a,b,c,d)a*exp(cls*b)+c*exp(cls*d) > > n2<-nls(proc~f(cls,a,b,c,d),data=bline,start=list(a=600,b=-.1,c=4,d=-. > 1),trace=TRUE) > proc~f(cls,a,b,c,d) > > but don't work! > > Thanks! > > > > On 10 April 2013 12:47, catalin roibu <catalinro...@gmail.com> wrote: > >> Hello! >> I try to nls and I compute a simple exponential equation, but the >> problem in nls is to anticipate the regression coefficients. >> >> >> On 10 April 2013 12:19, Jorge I Velez <jorgeivanve...@gmail.com> wrote: >> >>> Dear Catalin, >>> >>> You can look at ?nls. >>> >>> Alternatively, you could also consider a linear model as follows, >>> where "d" is your data: >>> >>> # plot your data >>> with(d, plot(cls, proc, las = 1)) >>> >>> # linear model >>> fit <- lm(proc ~ I(1/cls) + I((1/cls)^2), data = d) >>> summary(fit) >>> >>> # plotting >>> with(d, plot(cls, proc, las = 1)) >>> grid <- seq(min(d$cls), max(d$cls), length = 1000) points(grid, >>> predict(fit, data.frame(cls = grid)), type = "l", col = 2) >>> >>> HTH, >>> Jorge.- >>> >>> >>> >>> >>> On Wed, Apr 10, 2013 at 7:01 PM, catalin roibu <catalinro...@gmail.com>wrote: >>> >>>> Hello all! >>>> >>>> I have a problem with a double exponential equation. >>>> this are my data's> >>>> structure(list(proc = c(1870.52067384719, 766.789388745793, >>>> 358.701545859122, 237.113777545511, 43.2726259059654, >>>> 148.985133316262, 92.6242882655781, 88.4521557193262, >>>> 56.6404686159112, 27.0374477259404, 34.3347291080268, >>>> 18.3226992991316, 15.2196612445747, 5.31600719692165, >>>> 16.7015717397302, 16.3923389973684, 24.2702542054496, >>>> 21.247247993673, 18.3070717608672, 2.8811892177331, >>>> 3.18018869564679, 8.74204132937479, 7.11596966047229 ), cls = >>>> c(0.25, 0.5, 0.75, 1, 1, 1.5, 2, 2.5, 3, 3.5, 4, 4.5, 5, 5.5, 6, >>>> 6.5, 7, 7.5, 8, 8.5, 9, 9.5, 10)), .Names = c("proc", "cls"), >>>> row.names = c("0.25", "0.5", "0.75", "1", "11", "1.5", "2", "2.5", >>>> "3", "3.5", "4", "4.5", "5", "5.5", "6", "6.5", "7", "7.5", "8", >>>> "8.5", "9", "9.5", "10"), class = "data.frame") I want to compute a double exponential equation like this: >>>> proc=a*exp(b*class)+c*exp(d*class) >>>> or >>>> proc=a*exp(b*class)+c*class >>>> or a power, logarithmic equation. >>>> Is there a possibility to calculate R squared for each model? >>>> >>>> Thank you! >>>> >>>> -- >>>> --- >>>> Catalin-Constantin ROIBU >>>> Lecturer PhD, Forestry engineer >>>> Forestry Faculty of Suceava >>>> Str. Universitatii no. 13, Suceava, 720229, Romania >>>> office phone +4 0230 52 29 78, ext. 531 >>>> mobile phone +4 0745 53 18 01 >>>> +4 0766 71 76 58 >>>> FAX: +4 0230 52 16 64 >>>> silvic.usv.ro >>>> >>>> [[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. >>>> >>> >>> >> >> >> -- >> --- >> Catalin-Constantin ROIBU >> Lecturer PhD, Forestry engineer >> Forestry Faculty of Suceava >> Str. Universitatii no. 13, Suceava, 720229, Romania >> office phone +4 0230 52 29 78, ext. 531 >> mobile phone +4 0745 53 18 01 >> +4 0766 71 76 58 >> FAX: +4 0230 52 16 64 >> silvic.usv.ro >> > > > > -- > --- > Catalin-Constantin ROIBU > Lecturer PhD, Forestry engineer > Forestry Faculty of Suceava > Str. Universitatii no. 13, Suceava, 720229, Romania > office phone +4 0230 52 29 78, ext. 531 > mobile phone +4 0745 53 18 01 > +4 0766 71 76 58 > FAX: +4 0230 52 16 64 > silvic.usv.ro > [[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.