Dear Petr, I think it's a feature. the formula interface also won't let you specify the slots of S4 objects in the model spec.
How about coef(nls(y~a*x^b, data=list(x=DF[,1], y=DF[,2]), start=list(a=3, b=.7))) ? On Thu, 26 Jun 2008, Petr PIKAL wrote: > Dear all > > Nobody responded to my previous post so far so I try with more offending > subject. > > I just encountered a strange problem with nls formula. I tried to use nls > in cycle but I was not successful. I traced the problem to some parse > command. > > Here is an example > > DF<-data.frame(x=1:10, y=3*(1:10)^.5+rnorm(10)) > > coef(lm(log(DF[,2])~log(DF[,1]))) > (Intercept) log(DF[, 1]) > 0.7437320 0.6831726 > # this works > > coef(nls(y~a*x^b, data=DF, start=list(a=3, b=.7))) > a b > 2.6412881 0.5545907 > # OK, this works too > > coef(nls(DF[,2]~a*DF[,1]^b, data=DF, start=list(a=3, b=.7))) > Error in parse(text = x) : unexpected end of input in "~ " > coef(nls(DF[,2]~a*DF[,1]^b, start=list(a=3, b=.7))) > Error in parse(text = x) : unexpected end of input in "~ " > # but this does not > > > Browse[1]> > debug: mf$formula <- as.formula(paste("~", paste(varNames[varIndex], > collapse = "+")), env = environment(formula)) > Browse[1]> > Error in parse(text = x) : unexpected end of input in "~ " > > > > Actually the problem is that with calling nls with DF[,n]~... varNames and > varIndex is not correctly specified. > > I am not sure if this behaviour is a bug or feature. If it is a feature, > please help me how to call variables from data frame > when using nls inside cycle > > for (i in ....) result[i,] <- coef(nls( ...., )) > > Thank you > Petr > > > sessionInfo() > R version 2.8.0 Under development (unstable) (2008-05-18 r45723) > i386-pc-mingw32 > > locale: > LC_COLLATE=Czech_Czech Republic.1250;LC_CTYPE=Czech_Czech > Republic.1250;LC_MONETARY=Czech_Czech > Republic.1250;LC_NUMERIC=C;LC_TIME=Czech_Czech Republic.1250 > > attached base packages: > [1] stats grDevices datasets utils graphics methods base > > other attached packages: > [1] nlme_3.1-88 lattice_0.17-7 fun_0.1 > > loaded via a namespace (and not attached): > [1] grid_2.8.0 tools_2.8.0 > > > Petr Pikal > [EMAIL PROTECTED] > 724008364, 581252140, 581252257 > > ______________________________________________ > 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.