I received also this message that did not show up here: This sounds like a problem in (linear) mixed effects models. Look into packages nlme (with the lme() function) and lme4 (function lmer()) for starters. What you have falls under the heading of longitudinal or repeated measures data. Both packages allow flexibility in the choice of within-unit covariance structure.
It seem that it is trickier than it seems. I cannot test the gls(density~year*stream,..) as I do not have replicates within stream, but only one measurement for each stream. I tried to compare via anova the two models: Mixed1 <- lme(density~year, data=mydata, random=~1|sector) Mixed2 <- lme(density~year, data=mydata, random=~1|year/sector) But I'm not sure I can fit the Mixed2 model. Many thanks for the answers so far. Any ideas? Simone Vincenzi, PhD Department of Environmental Sciences University of Parma Viale G. P. Usberti, 33/A, 43100 Parma, Italy Phone: +39 0521 905696 Fax: +39 0521 906611 e.mail: <mailto:svinc...@nemo.unipr.it> svinc...@nemo.unipr.it [[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.
