Balance metric that uses the Shannon-Wiener statistic of
information content. The b2 measure is given by the sum over the depths of
all tips, divided by 2^depth: sum Ni / 2^Ni.
Although also defined on non-binary trees, the treestats package only
provides code for binary trees.
Usage
b2(phy, normalization = "none")
Arguments
- phy
phylo object or ltable
- normalization
"none" or "yule", when "yule" is chosen, the statistic
is divided by the Yule expectation, following from theorem 3.7 in Bienvenu
2020.
Value
Maximum depth (in number of edges)
References
K.-T. Shao and R. R. Sokal. Tree Balance.
Systematic Zoology, 39(3):266, 1990. doi: 10.2307/2992186.
Bienvenu, François, Gabriel Cardona, and Celine Scornavacca.
"Revisiting Shao and Sokal’s $$ B_2 $$ B 2 index of phylogenetic balance."
Journal of Mathematical Biology 83.5 (2021): 1-43.