Dear listers, I am trying to fit a model using nlsList() using alternately a SSfol() selfstart function or its developped equivalent formulae.
This preliminary trial works well mydata<-groupedData(Conc~Tps|Organ,data=mydata) mymod1<-nls(Conc~SSfol(Dose,Tps,lKe,lKa,lCl),data=mydata) as well as a developped form: mymod2<-nls(Conc~Dose * exp(lKe+lKa-lCl) * (exp(-exp(lKe)*Tps)-exp(-exp(lKa)*Tps)) /(exp(lKa)-exp(lKe)), data=mydata, start= c(lKe=-2.77, lKa=-1.41, lCl=-1.13) ) However when trying to fit the model with nlsList, I get: mymod3<-nlsList(Conc~Dose * exp(lKe+lKa-lCl) * (exp(-exp(lKe)*Tps)-exp(-exp(lKa)*Tps)) /(exp(lKa)-exp(lKe)), data=mydata, start= c(lKe=-2.77, lKa=-1.41, lCl=-1.13) ) Error in model.frame(formula, rownames, variables, varnames, extras, extranames, : variable lengths differ Error in model.frame(formula, rownames, variables, varnames, extras, extranames, : variable lengths differ Error in model.frame(formula, rownames, variables, varnames, extras, extranames, : variable lengths differ Or specifying the grouping factor explicitely: mymod3<-nlsList(Conc~Dose * exp(lKe+lKa-lCl) * (exp(-exp(lKe)*Tps)-exp(-exp(lKa)*Tps)) /(exp(lKa)-exp(lKe))|Organ, data=mydata, start= c(lKe=-2.77, lKa=-1.41, lCl=-1.13) ) Error in model.frame(formula, rownames, variables, varnames, extras, extranames, : variable lengths differ Error in model.frame(formula, rownames, variables, varnames, extras, extranames, : variable lengths differ Error in model.frame(formula, rownames, variables, varnames, extras, extranames, : variable lengths differ I cannot find out why the grouping factor cannot be used (it has the same length as the other variables...) Another strange thing occurs: in the example given in the help of nlsList.selfstart, the following command works well: fm1 <- nlsList(SSasympOff, CO2) However its seemingly equivalent applied to the case above fails: mymod4<-nlsList(SSfol,data=mydata) Error in eval(expr, envir, enclos) : object "input" not found Error in eval(expr, envir, enclos) : object "input" not found Error in eval(expr, envir, enclos) : object "input" not found Any hint/suggestion appreciated. Kind regards, Patrick Giraudoux ______________________________________________ R-help@stat.math.ethz.ch mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide! http://www.R-project.org/posting-guide.html