Dear R-Sig-Phylo Group,
I had a question regarding the calculation of regression statistics using
PGLS. When I obtain the degrees of freedom from a PGLS object using ape in
R, I notice that it returns the same number of degrees of freedom as under
OLS, and the AIC of a bivariate function is calculated under the assumption
that k=2 (i.e., that the same number of degrees of freedom are used as in
the OLS). Does anyone know why this is? I would have thought that a PGLS
would have eaten up a greater number of degrees of freedom than OLS, if for
no other reason than it constrains the motion of the system by adding
phylogenetic covariation in as an additional variable, and thus would be
expected to eat up at least one additional degree of freedom in the same
way that adding additional categorical or quantitative variables would?
Sincerely,
Russell
[[alternative HTML version deleted]]
_______________________________________________
R-sig-phylo mailing list - R-sig-phylo@r-project.org
https://stat.ethz.ch/mailman/listinfo/r-sig-phylo
Searchable archive at http://www.mail-archive.com/r-sig-phylo@r-project.org/
