Hello folks, Only one point here:
On 18/04/2013, at 15:52 PM, Pierre THIRIET wrote: > > > Pay attention in using NMDS. As you said, it is rank-based, this is why > fitting environmental vectors to NMDS biplot is not so appropriate, despite > widely done. I don't see the problem about ordisurf and PCoA or CAP: Ordisurf > enables you to fit environnemental variables that have non-linear > relationships with PC of distance based ordinations. This is not true. I have seen this sometimes in Internet, but this really is not true: The NMDS ordination space is strictly *metric*. In vegan it is even strictly *Euclidean*. So it is absolutely correct to fit vectors to NMDS ordination. (In MASS::isoMDS you can also have any Minkowski metric, but only Euclidean or Minkowski with exponent=2 is allowed in vegan even with isoMDS.) What is non-metric is the monotonic regression from *metric* ordination to any dissimilarity measure. So NMDS finds metric solution from any dissimilarity measure. I -- Jari Oksanen, Dept Biology, Univ Oulu, 90014 Finland jari.oksa...@oulu.fi, Ph. +358 400 408593, http://cc.oulu.fi/~jarioksa _______________________________________________ R-sig-ecology mailing list R-sig-ecology@r-project.org https://stat.ethz.ch/mailman/listinfo/r-sig-ecology
