Great, thanks for your reply! I've just tracked down a copy of Pinheiro & Bates (2000) so I'll look at that, too.
Thanks again, Mark On Fri, Aug 22, 2008 at 9:56 AM, Christoph Scherber < [EMAIL PROTECTED]> wrote: > Dear Mark, > > I would include the repeated measure as the smallest stratum in the random > effects specification: > > random=~1|sampleunit/year > > Setting up user-defined variance structures should be possible using for > example: > > weights=varPower(form=~habitat) > > or also try out the available corStruct() classes (found in Pinheiro and > Bates 2000) > > HTH > Christoph > > > > > Mark Na schrieb: > >> Hello, >> >> We are attempting to use nlme to fit a linear mixed model to explain bird >> abundance as a function of habitat: >> >> >> lme(abundance~habitat-1,data=data,method="ML",random=~1|sampleunit) >> >> The data consist of repeated counts of birds in sample units across >> multiple >> years, and we have two questions: >> >> 1) Is it necessary (and, if so, how) to specify the repeated measure >> (years)? As written, the above code does not. >> >> 2) How can we specify a Toeplitz heterogeneous covariance structure for >> this >> model? We have searched the help file for lme, and the R-help archives, >> but >> cannot find any pertinent information. If that's not possible, can we >> adapt >> an existing covariance structure, and if so how? >> >> Thanks, Mark >> >> [[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. >> >> . >> >> > -- > Dr. rer.nat. Christoph Scherber > University of Goettingen > DNPW, Agroecology > Waldweg 26 > D-37073 Goettingen > Germany > > phone +49 (0)551 39 8807 > fax +49 (0)551 39 8806 > > Homepage http://www.gwdg.de/~cscherb1 <http://www.gwdg.de/%7Ecscherb1> > [[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.
