Dear All, I am trying to fit the following model in nlsLM():
fn5 <- function(x, T, t1, w_inf, Lt0){ S<-function(x, T, t1){ x+(1-T)/(2*pi)*sin(2*pi*(x-t1)/(1-T)) } F <- function(x, T, t1){ t2 <- t1 + (1-T)/2 t3 <- t1 + (1+T)/2 t.factorial <- x%%1 floor(x)*(1-T) + S(t.factorial, T, t1)*(0<=t.factorial & t.factorial<t2) + S(t2, T, t1)*(t2<=t.factorial & t.factorial<t3) + S(t.factorial-T, T, t1)*(t3<=t.factorial & t.factorial<1) } return(w_inf - (w_inf - Lt0)*exp(-(2/30)*(F(x,T,t1)-F(7,T,t1)))) } fn6<- y~fn5(x, T, t1, w_inf, Lt0) startval<-c(x=x, T=0.035, t1=0.359, w_inf=135, Lt0=47) (nlsktm1 <- nlsLM(fn6, start=startval, lower=c(x=x, T=0.0135, t1=0.259, w_inf=131, Lt0=41), jac=NULL, trace=T, data=ktm, control=nls.control(maxiter=10))) When I run the above script, the following error is displayed: Error in nlsModel(formula, mf, start, wts) : singular gradient matrix at initial parameter estimates In addition: Warning message: In nls.lm(par = start, fn = FCT, jac = jac, control = control, lower = lower, : lmdif: info = 0. Improper input parameters. Suitable help is requested. -- Dr. TR Chandrasekhar, M.Sc., M. Tech., Ph. D., Sr. Scientist Rubber Research Institute of India Hevea Breeding Sub Station Kadaba - 574 221 DK Dt., Karnataka Phone-Land: 08251-214336 Mobile: 9448780118 [[alternative HTML version deleted]] ______________________________________________ R-help@r-project.org 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.