This function computes the balance of a phylogenetic tree, that is for each node of the tree the numbers of descendants (i.e. tips) on each of its daughter-branch. The tree must be fully dichotomous.
balance(phy)an object of class "phylo".
a numeric matrix with two columns and one row for each node of the
tree. The columns give the numbers of descendants on each
daughter-branches (the order of both columns being arbitrary). If the
phylogeny phy has an element node.label, this is used as
rownames for the returned matrix; otherwise the numbers (of mode
character) of the matrix edge of phy are used as rownames.
Aldous, D. J. (2001) Stochastic models and descriptive statistics for phylogenetic trees, from Yule to today. Statistical Science, 16, 23--34.