Jari, Thank you for the quick reply. Maybe I should use something like PCNM first with the lat/long data to then use in the rda? I really appreciate all of your help. Are there anyother/better ways to account for spatial autocorrelation. I guess I need to show that spatial autocorellation exists and then if it does account for it? Any reading etc. would be greatly appreciated. I appreciate all of the help. kindest regards,
Stephen P.S. I will let you know about the stepwise selection and scope argument On Wed, Jul 10, 2013 at 2:28 PM, Jari Oksanen <jari.oksa...@oulu.fi> wrote: > > On 10/07/2013, at 21:00 PM, Stephen Sefick wrote: > > > Hello all, > > > > I would like to run this by everyone and maybe get some hints as to what > R functions I could use for this. Ok, so I have macroinvertebrate > assemblage data from across the SE. I would like to control for geographic > distance (lat/long), Watershed area, and year before submitting these data > to an RDA with the rest of the environmental data using a variable > selection technique. > > > > Does it make sense to detrend the data using a mlm on hellinger > transfomed abundances with the above env variables as regressors and then > submit the residuals to rda with the rest of the env variables I am > interested in? > > > Stephen, > > If you happen to use vegan functions for forward selection, please note > that they all (should) take a scope argument that can (should) be a list of > lower and upper scopes. Put your controlled variables (distance???, > watershed area, year) in the lower scope and these plus other candidate > variables in the upper scope, and there you go. I have used "should", > because I have rarely used these functions myself, and I'm not sure if > lower scope really is implemented in all, but is *should* be: file a bug > report if this fails. > > I have no idea how to have distance RDA. Well, I have ideas, but none that > I have are very good. > > Using separate mlm and modelling residuals will not work quite correctly, > because that ignores correlations between groups of variables. Vegan > functions do not ignore those. > > Cheers, Jari Oksanen > -- > Jari Oksanen, Dept Biology, Univ Oulu, 90014 Finland > jari.oksa...@oulu.fi, Ph. +358 400 408593, http://cc.oulu.fi/~jarioksa > > > > > > [[alternative HTML version deleted]] _______________________________________________ R-sig-ecology mailing list R-sig-ecology@r-project.org https://stat.ethz.ch/mailman/listinfo/r-sig-ecology
