sym_nodes {treestats}

Symmetry nodes metric

Description

Balance metric that returns the total number of internal nodes that are not-symmetric (confusingly enough). A node is considered symmetric when both daughter trees have the same topology, measured as having the same sum of depths, where depth is measured as the distance from the root to the node/tip.

Usage

sym_nodes(phy, normalization = "none")

Arguments

phy

phylo object or ltable

normalization

"none" or "tips", in which case the resulting statistic is divided by the number of tips - 2 (e.g. the maximum value of the symmetry nodes index for a tree).

Value

Maximum depth (in number of edges)

References

S. J. Kersting and M. Fischer. Measuring tree balance using symmetry nodes — A new balance index and its extremal properties. Mathematical Biosciences, page 108690, 2021. ISSN 0025-5564. doi:https://doi.org/10.1016/j.mbs.2021.108690