Automatically resizing the tip labels of a plotted tree

It just occurred to me that it might be useful for some users if the font size for our tree by default scaled automatically with the number of tips in our tree and the dimensions of our open plotting device.

Here's a code chunk that will do this. It's very simple:

foo<-function(tree,...){
    fsize<-36*par()$pin[2]/par()$pin[1]/Ntip(tree)
    plotTree(tree,fsize=fsize,lwd=1,...)
}

I chose 36 as the number of taxa to measure against, because 36 results in a nice tip label spacing for cex=1.0 with the stardard plotting device dimensions. E.g.:

library(phytools)
tree<-pbtree(n=36)
plotTree(tree)

Let's try some different tree sizes:

foo(pbtree(n=20))

foo(pbtree(n=80))

data(anoletree)
foo(anoletree,ftype="i")

The piece par()$pin[2]/par()$pin[1] computes the aspect ratio of the current plotting device so that the font can be resized as appropriate. For example (for a 6 W by 10.5 H plot area):

foo(anoletree,ftype="i")

or (for a plot area shorter than it is tall):

foo(pbtree(n=40))

It is imperfect, in large part because (depending on our plotting device) the plotted font size does not actually change continuously in R.

I'm going to use this in another new phytools plotting function shortly.

That's it.