Data for: Correlated evolution of categorical characters under a simple model

I describe a simple model for quantifying the strength of association
between two categorical characters evolving on a phylogenetic
tree. The model can be used to estimate a correlation statistic
that asks whether or not the two characters tend to change at the
same time (positive correlation) or at different times (no
correlation). This is different than asking if changes in one
character are associated with a particular state in
another character, which has been the focus of most prior tests
for phylogenetic correlation in categorical characters. Analyses
of simulated data indicate that positive correlations can be
accurately estimated over a range of different tree sizes and
phylogenetic signals.