I am interested in making a figure like this:
Where I have either an NMDS or a PCOA biplot (or loading plot I've seen it called), where the arrows represent the strength and direction of certain metadata variables that explain microbiome variation. In my case I have a factor, diet, where I would like different arrows representing the levels of my diet factor. So an herbivory arrow, a carnivory arrow and so forth, pointing to each cluster on my PCOA. I've seen ways to do this for numerical variables but not categorical. If anyone can point me in the right direction I would be forever indebted!