Hi, I've got the following data:
x<-c(1,3,5,7) y<-c(37.98,11.68,3.65,3.93) penetrationks28<-dataframe(x=x,y=y) now I need to fit a non linear function so I did: fit <- nls(y ~ I(a+b*exp(1)^(-c * x)), data = penetrationks28, start = list(a=0,b = 1,c=1), trace = T) The error message I get is: Error in nls(y ~ I(a + b * exp(1)^(-c * x)), data = penetrationks28, start = list(a = 0, : singular gradient I've tried to change the startervalues but it always gives the same error I've also tried the following adjustment hoping that the c value would be negative: fit <- nls(y ~ I(a+b*exp(1)^(c * x)), data = penetrationks28, start = list(a = 1,b = 1,c=1), trace = T) but then the error message is: Error in nls(y ~ I(a + b * exp(1)^(c * x)), data = penetrationks28, start = list(a = 1, : number of iterations exceeded maximum of 50 What can I do ? Thanks in advance -- View this message in context: http://r.789695.n4.nabble.com/nls-function-tp4546791p4546791.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.
