Hi, I have great problems with my work in R. I look for to model the growth of fish. I have "Longitudinal data", a serie of repeated measures for each individual. Using the corresponding packages "nlme" in R. I treat to fit to the data different growth functions, wich were entered by me. Unfortunately for no it was arrived at the convergence, several error messages appeared. I am going to display the growth functions so as they were entered and a "nlme" call example: # differents growth function #vonBertlalanffy vonBert<- function(x, Linf, K, t0) Linf*(1-exp(-K*(x-t0))) size ~ vonBert(age, Linf, K,t0) vonBert <-deriv(~ Linf*(1-exp(-K*(x-t0))), c("Linf","K","t0"),function(x,Linf,K,t0){}) vonBertInit <- function(mCall, LHS, data) { xy <- sortedXyData(mCall[["x"]], LHS, data) Linf <- 900 if (Linf != max(xy[,"y"])) Linf <- -Linf K <- 0.3 t0<-0 value <- c(Linf, K, t0) names(value) <- mCall[c("Linf", "K","t0")] value } vonBert <- selfStart(vonBert, initial = vonBertInit) class(vonBert) #Richards Rich <- function(x, Linf, K, t0, m) Linf*(1-exp(-K*(x-t0)))^(1/(1-m)) size ~ Rich(age, Linf, K, t0, m) Rich <-deriv(~ Linf*(1-exp(-K*(x-t0)))^(1/(1-m)), c("Linf","K","t0","m"),function(x,Linf,K,t0,m){}) RichInit <- function(mCall, LHS, data) { xy <- sortedXyData(mCall[["x"]], LHS, data) Linf <- 900 if (Linf != max(xy[,"y"])) Linf <- -Linf K <- 0.3 t0<-0 m <- 0.3 value <- c(Linf, K, t0, m) names(value) <- mCall[c("Linf", "K","t0","m")] value } Rich <- selfStart(Rich, initial = RichInit) class(Rich) #call Rich.nlme <- nlme(size ~ Rich(age, Linf, K, t0, m), data = L.gd, fixed = Linf + K +t0 +m~ 1, start = list(fixed = c(900, 0.3,-3,0.9))) #error message Error: Singularity in backsolve at level 0, block 1 In addition: Warning message: NaNs produced in: log(x) What is the problem? I do not understand that it is what is bad: the data, the entered growth functions, some specification... I will thank for any contribution of information. Lic. Gabriela Escati Pe?aloza Biolog?a y Manejo de Recursos Acu?ticos Centro Nacional Patag?nico(CENPAT). CONICET Bvd. Brown s/n?. (U9120ACV)Pto. Madryn Chubut Argentina Tel: 54-2965/451301/451024/451375/45401 (Int:277) Fax: 54-29657451543 _________________________________________________________ Hor?scopos, Salud y belleza, Chistes, Consejos de amor: el contenido m?s divertido para tu celular est? en Yahoo! M?vil. Obtenelo en http://movil.yahoo.com.ar