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.
sym_nodes(phy, normalization = "none")Maximum depth (in number of edges)
phylo object or ltable
"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).
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