See this post: http://r.789695.n4.nabble.com/varIdent-error-using-gam-function-in-mgcv-td2260556.html
Kevin On Tue, Oct 1, 2013 at 4:37 PM, Sonya Odsen <od...@ualberta.ca> wrote: > I'm running R version 3.0.2 (2013-09-25) on a Windows computer. > Here is a simplified version of my data: > > a <- expand.grid(SITE=c("A","B"),TREAT=c("low","med","high"), REP=c(1:5)) > VAR <- round(rep(c(10,12,14,15,17,18),5)+rnorm(30)*2,1) > dat <- cbind(a,VAR) > > I'm running a GAM on my data (package: mgcv, version 1.7.12). My initial > model is of the form: > > M1 <- gam(VAR ~ SITE + TREAT, > data = dat) > > Model validation shows heterogeneity in Residuals vs. Treatment (in my true > dataset, not the demo), so I want to apply a weighted variance structure to > my gam, following examples given in Zuur (2009), using function varIdent > (package: nlme, version 3.1.102): > > M2 <- gam(VAR ~ SITE + TREAT, > weights = varIdent(form=~1|TREAT), > data = dat) > > Given examples from the help files and books, I expect this to run as-is. > Instead, Running the gam returns the following error message: > > Error in model.frame.default(formula = VAR ~ SITE + TREAT, data = dat, : > variable lengths differ (found for '(weights)') > > > varIdent(form=~1|TREAT) > Variance function structure of class varIdent with no parameters, or > uninitialized > > > coef(varIdent(form=~1|TREAT)) > numeric(0) > > > This behavior of varIdent() is unlike anything I've seen in examples, in > the helpfile or in textbooks. I would be grateful for any help. > > Regards, > Sonya Odsen > > > --- > Sonya Odsen > M.Sc. Candidate > University of Alberta > Dept. of Renewable Resources > od...@ualberta.ca > > [[alternative HTML version deleted]] > > ______________________________________________ > 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. > -- Kevin Wright [[alternative HTML version deleted]] ______________________________________________ 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.