Sackin index of (im)balance.

The Sackin index is calculated as the sum of ancestors for each of the tips. Higher values indicate higher imbalance. Two normalizations are available, where a correction is made for tree size, under either a Yule expectation, or a pda expectation.

Usage

sackin(phy, normalization = "none")

Arguments

phy

phylogeny or ltable

normalization

normalization, either 'none' (default), "yule" or "pda".

Value

Sackin index

References

M. J. Sackin (1972). "Good" and "Bad" Phenograms. Systematic Biology. 21:225-226.

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)
sackin(balanced_tree)
#> [1] 34
sackin(unbalanced_tree) # should be much higher
#> [1] 54