Hi Pascal,
The assumption of normality in GLS, as in OLS, concerns the residuals
not the data. A recent reference on this issue is:
Alain F. Zuur, Elena N. Ieno and Chris S. Elphick: A protocol for data
exploration to avoid common statistical problems. Methods in Ecology &
Evolution 2010, 1, 3–14. doi: 10.1111/j.2041-210X.2009.00001.x
To answer your specific question, I'm not aware of such nonparametric
method though a Monte Carlo procedure might be feasible.
Best,
Emmanuel
Pascal Title wrote on 11/05/2012 10:46:
Hi everyone
I have character data for species on a phylogeny, but simple
transformations like log-transformations or square-root transformations are
not proving to be sufficient to get the data to be normal. If this were a
non-phylogenetic test, I would resort to something like a Spearman
correlation, which is non-parametric.
But with phylogenetic generalized least squares, is there any method that
is nonparametric?
Thanks!
-Pascal Title
--
Emmanuel Paradis
IRD, Jakarta, Indonesia
http://ape.mpl.ird.fr/
_______________________________________________
R-sig-phylo mailing list
R-sig-phylo@r-project.org
https://stat.ethz.ch/mailman/listinfo/r-sig-phylo
