Description Usage Arguments Value Author(s) References Examples
This function calculates the Sackin index S(T) for a given rooted tree T. The tree must not necessarily be binary. S(T) is defined as
S(T)=∑_{x in V_L(T)} depth(x)=∑_{u in V_in(T)} (n_u)
in
which V_L(T) denotes the leaf set of T, depth(x)
denotes the depth of the leaf x, V_in(T) denotes the set of
inner vertices in T and n_u denotes the number of leaves
in the pending subtree that is rooted at u. The Sackin index is an
imbalance index.
For n=1 the function returns S(T)=0 and a warning.
1 | sackinI(tree)
|
tree |
A rooted tree in phylo format. |
sackinI
returns the Sackin index of the given tree.
Luise Kuehn
M.J. Sackin. "Good" and "Bad" Phenograms. Systematic Biology, 21(2):225-226, 1972. doi: 10.1093/sysbio/21.2.225.
K.-T. Shao and R.R. Sokal. Tree Balance. Systematic Zoology, 39(3):266, 1990. doi: 10.2307/2992186.
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