How do I place labels within opaque text boxes at group centroids in ordiellipse?

Question

I'm trying to place labels within opaque text boxes at my group centroids in vegan::ordiellipse().

Code below yields plot below. Note that centroid labels default to plain text with no opaque text box.

library(vegan)

ordiplot(jac_pcoa, main = Trt) 
ordiellipse(jac_pcoa, 
        draw = "polygon",
        kind = "se",
        groups = pcoa_grps, 
        col = col_vect,
        lwd = 2)
ordiellipse(jac_pcoa, groups = pcoa_grps, 
        kind = "ehull", 
        col = col_vect,
        lwd = 2,
        label = TRUE)

Function vegan::ordispider(), however, formats the labels as I want.

ordiplot(jac_pcoa, main = i) 
ordispider(jac_pcoa, groups = pcoa_grps, 
            col = col_vect,
            lwd = 2,
            label = TRUE)

How can I achieve labels like those generated by ordispider() when using ordiellipse()?

Answer 1

There is no option to do this directly, but you can trick the function to do what you want: ordiellipse will draw labels on opaque labels with draw = "polygon". Setting col=NULL or omitting the col argument will only draw non-filled ellipses, and the colour of the border line can be set with argument border.