Why are you doing this instead of using the survival package? Bert
On Tuesday, April 28, 2015, Hanze Zhang <[email protected]> wrote: > Hi, R users, > > > I am using nlm function to get the MLE of parameter alpha and lambda from a > parametric survival model (Weibull distribution). However, this message > always came out: ' invalid function value in 'nlm' optimizer'. Could anyone > help me? Code is > > project<-read.table(file="C://data.txt", header=T, as.is=T) > names(project) > attach(project) > > x<-time > delta<-ind > > > # -log likelihood > #alpha<-theta[1] > #lambda<-theta[2] > ln<-function(theta) > { > > > > -sum(delta)*log(theta[1]*theta[2])-sum(delta)*(theta[1]-1)*log(x[delta==1])+theta[2]*sum(x^theta[1]) > } > > #MLE > nlm(ln,theta<-c(1,1),hessian=TRUE) > > > Thanks! > > [[alternative HTML version deleted]] > > ______________________________________________ > [email protected] <javascript:;> mailing list -- To UNSUBSCRIBE and > more, see > 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. > -- Bert Gunter Genentech Nonclinical Biostatistics (650) 467-7374 "Data is not information. Information is not knowledge. And knowledge is certainly not wisdom." Clifford Stoll [[alternative HTML version deleted]] ______________________________________________ [email protected] mailing list -- To UNSUBSCRIBE and more, see 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.
