Corrected Colless index of (im)balance.

The Corrected Colless index is calculated as the sum of \(abs(L - R)\) over all nodes, corrected for tree size by dividing over (n-1) * (n-2), where n is the number of nodes.

Usage

colless_corr(phy, normalization = "none")

Arguments

phy

phylo object or ltable

normalization

A character string equals to "none" (default) for no normalization or "yule", in which case the obtained index is divided by the Yule expectation.

Value

corrected colless index

References

Heard, Stephen B. "Patterns in tree balance among cladistic, phenetic, and randomly generated phylogenetic trees." Evolution 46.6 (1992): 1818-1826.

Examples

simulated_tree <- ape::rphylo(n = 10, birth = 1, death = 0)
balanced_tree <- treestats::create_fully_balanced_tree(simulated_tree)
unbalanced_tree <- treestats::create_fully_unbalanced_tree(simulated_tree)
colless_corr(balanced_tree)
#> [1] 0.1111111
colless_corr(unbalanced_tree) # should be higher
#> [1] 1