HongSheng Liao wrote: > w.age.female.2004 <- nls(WEIGHT ~ (alpha*TOTAL^beta)/454, > start=list(alpha=1, beta=3), > data=spottedseatrout2004.female.data) > > I am trying to fit above model to length-weight data of a fish species > (spotted seatrout) by year (1999-2006). The convergence occurred for all > the years except 2002 and 2004. In these two year, R shows the error > called 'singular gradient' in the model. Could anyone please help me to > fix the error? I don't think there are any problems with my data because I > can fit the same model to 2004 data without any problems using SAS. Thank > you very much in advance. > If your starting values are poor, it can be a toss-up whether nls() converges or not. One idea is to try the PORT algorithm, another is to get better starting values from cf <- coef(lm(log(WEIGHT*454)~log(TOTAL))) start = list(alpha=exp(cf[1]), beta=cf[2]) > Hongsheng (Hank) Liao, Ph.D. > Lab Manager > Center for Quantitative Fisheries Ecology > 800 West 46th Street > Old Dominion University > Norfolk, Virginia 23508 > Phone:757.683.4571 > Fax:757.683.5293 > > ______________________________________________ > 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. >
-- O__ ---- Peter Dalgaard Øster Farimagsgade 5, Entr.B c/ /'_ --- Dept. of Biostatistics PO Box 2099, 1014 Cph. K (*) \(*) -- University of Copenhagen Denmark Ph: (+45) 35327918 ~~~~~~~~~~ - ([EMAIL PROTECTED]) FAX: (+45) 35327907 ______________________________________________ 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.
