Thanks for Emmanual.
Kate, I think the original explanation of dummy variables with independent
contrasts is here:
Garland Jr. T., P.H. Harvey, and A.R. Ives. 1992. Procedures for the analysis
of comparative data using phylogenetically independent contrasts. Systematic
Biology 41:18–32.
Hi Kate,
You can compute PICs for a categorical variable in the same way than
you enter it in a linear model, that is by first computing its
"contrasts" (this is different from the "P-I-Contrasts", though both
have some conceptual similarities). The easiest way to do it is to use
the
