I am running the following nls equation. I tried it with data that excel was fitting and got the error: singular gradient matrix at initial parameter estimates I thought it was due to a low number of points (6), but when I create a dataset, I get the same problem. If I remove the parameter "a," then it can find a solution. Does anyone know what I can do to fit this model?
vardata<- rnorm(73,mean=0,sd=5) x<-0:72 a<-1 b<-50 k<-0.05 l<-5 startt<-c(a,b,k,l) yf<-a+b*(1-exp(-k*(x-l))) y<-yf+vardata nmodel<-nls(y~a+b*(1-exp(-k*(x-l))), start=list(a=1,b=50,k=0.05,l=5)) -- View this message in context: http://r.789695.n4.nabble.com/nls-help-tp3328521p3328521.html Sent from the R help mailing list archive at Nabble.com. ______________________________________________ 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.
