Steve: Obviously, you would do better to consult a local statistician. Presumably, you have none, so you would probably do better posting on appropriate R SIGs -- e.g. R-sig-mixed-models, R-sig-ecology and the liike. R-help is really not designed for this (although good souls sometimes respond). In a similar vein, you might try seacrhing the net for non-R statistical lists that might be helpful.
-- Bert On Fri, Nov 12, 2010 at 5:40 AM, <steve_fried...@nps.gov> wrote: > > Hi, > > This is a question regarding technique rather than an R specific issue. I > have been asked to evaluate a 30+ year long term continuous survey of bird > presence/absence data that has an associated ocular estimate of the > vegetation community percent coverage. The data are organized by > subpopulations (5), and by year ( 1991 - present). We are interested in > gaining understanding on whether bird presence is 1) related to vegetation > community cover and 2) whether that relationship is variable over the > period of record. Ultimately I can associate management to this, but that > data has not be pulled together yet for this survey. > > My first thought was to simply look to a clustering and nmds to examine > which sites were more similar given the vegetation community. Following > this I had intended to repeat that analysis using year as a grouping > variable to see if the clusters change. This would then provide the basis > for a trajectory analysis. > > Ok, so that might be rather very simple, I'm now considering a repeated > measures approach, but do not have much experience here. Since every site > is the same in all years, what changes is the bird count and perhaps the > vegetation community coverage estimates. > > Can someone let me know if this alternate approach is a better approach and > how to conduct the analysis in R? > > Thanks very much. If additional information is needed I can provide it, > but I didn't want to fill mail boxes with unnecessary info at this time. > > Steve > > Steve Friedman Ph. D. > Spatial Statistical Analyst > Everglades and Dry Tortugas National Park > 950 N Krome Ave (3rd Floor) > Homestead, Florida 33034 > > steve_fried...@nps.gov > Office (305) 224 - 4282 > Fax (305) 224 - 4147 > > ______________________________________________ > 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. > -- Bert Gunter Genentech Nonclinical Biostatistics ______________________________________________ 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.
