I understand that PICs are normally only used for continuous traits. However, on this how-to site (https://www.r-phylo.org/wiki/HowTo/Phylogenetic_Independent_Contrasts) there is mention of "Discrete traits can be coded as continuous variables (see ?contr.treatment) and analysed as usual, if they are independent (explanatory) variables."
However, I'm having trouble understanding the commands described in ?contr.treatment and how they relate at all to using discrete traits in PICs. I assume it is a way to transform discrete into continuous data (or at least the appearance of cont. data) so as to perform the PIC, but I don't know how to get there from that hint.
This would very much help analyze my data, which includes both continuous and discrete data. I've already performed a phylogenetic logistic regression, but I feel that PICs could help cement my case if possible to perform.