You can use them, but you shouldn't use them individually. Directions in NMDS aren't like the independent (orthogonal) components of PCA or CA. You need the distances in *both* (assuming k = 2, *all* for k > 2) NMDS dimensions to recover the solution. Also directions across and up/down the NMDS diagram are arbitrary - we can rotate the solution and the solution remains the same.
What vegan does here is to use the coordinates in NMDS dimensions 1 and 2 (or 1,...,k) as predictors for a single response variable. This is a bit silly - the models then says that the locations in the ordination space *influence* the response variable! But if there is such a relationship, it suggests the converse, that the response varies over the gradients in the ordination. G On Mon, 2013-06-10 at 08:37 +0000, Paolo Piras wrote: > Hi, > actually I think you CAN use them (as predictors or response either) > because, albeit in its unique way, NMDS **IS** a method to summarize a > highly multidimensional phenomenon. > best > paolo > ________________________________________ > Da: r-sig-ecology-boun...@r-project.org [r-sig-ecology-boun...@r-project.org] > per conto di Simone Ruzza [simone.ruzz...@gmail.com] > Inviato: lunedì 10 giugno 2013 10.26 > A: r-sig-ecology@r-project.org > Oggetto: Re: [R-sig-eco] simple question about nmds > > Apolologies, I re-phrase what I have said before: I would be interested > using the site scores within a multiple regression settings, but the the > scores a response rather than predictors. > > Best wishes, > > Simone > > > On Mon, Jun 10, 2013 at 9:19 AM, Simone Ruzza <simone.ruzz...@gmail.com>wrote: > > > Dear list, > > > > apologies for the total beginner's question. I was wondering whether > > one can use the site scores of an NMDS ordination to do do further > > analyses as typically done for other ordination methods, e.g. use the > > axis scores as predictors in a multiple regression settings. I think > > it should not be possible, because the aim of NMDS is not to summarize > > the major patterns of variations withing a multivariate dataset. Do > > you confirm? > > > > thanks in advance, > > > > Simone > > > > [[alternative HTML version deleted]] > > _______________________________________________ > R-sig-ecology mailing list > R-sig-ecology@r-project.org > https://stat.ethz.ch/mailman/listinfo/r-sig-ecology > > > _______________________________________________ > R-sig-ecology mailing list > R-sig-ecology@r-project.org > https://stat.ethz.ch/mailman/listinfo/r-sig-ecology > -- Gavin Simpson, PhD [t] +1 306 337 8863 Adjunct Professor, Department of Biology [f] +1 306 337 2410 Institute of Environmental Change & Society [e] gavin.simp...@uregina.ca 523 Research and Innovation Centre [tw] @ucfagls University of Regina Regina, SK S4S 0A2, Canada _______________________________________________ R-sig-ecology mailing list R-sig-ecology@r-project.org https://stat.ethz.ch/mailman/listinfo/r-sig-ecology