RootNodeDistance()
calculates the number of nodes between the chosen leaf
and the root of tree
.
This is an unsatisfactory measure, as the range of possible
distances is a function of the shape of the tree.
As an example, leaf X1 in the tree (.,(.,(.,(.,(X1,(a,b))))))
falls outside the clade (a, b) and has a root-node distance of 4,
whereas leaf X2 in the tree (.,((.,(.,.)),(b,(X2,a))))
falls within the clade (a, b), so should be considered more 'crownwards',
yet has a smaller root-node distance (3).
Stemwardness.pngTreeTools
par(mfrow = c(1, 2), mar = rep(0.3, 4))
plot(ape::read.tree(text="(.,(.,(.,(.,(X1,(a,b))))));"))
ape::nodelabels(1:4, 9:12)
ape::edgelabels(1:2, 11:12)
plot(ape::read.tree(text="(.,((.,(.,.)),(b,(X2,a))));"))
ape::nodelabels(1:3, c(9, 12, 13))
ape::edgelabels(1, 12)
SisterSize()
measures the number of leaves in the clade that is sister to
the chosen leaf. In the examples above, X1 has a sister size of 2 leaves,
whereas X2, which is 'more crownwards', has a smaller sister size (1 leaf),
as desired.