sackinI {treebalance} | R Documentation |
Calculation of the Sackin index for rooted trees
Description
This function calculates the Sackin index for a given rooted
tree
. The tree must not necessarily be binary.
is defined as
in
which denotes the leaf set of
,
denotes the depth of the leaf
,
denotes the set of
inner vertices in
, and
denotes the number of leaves
in the pending subtree that is rooted at
. The Sackin index is an
imbalance index.
For the function returns
and a warning.
For details on the Sackin index, see
also Chapter 5 in "Tree balance indices: a comprehensive survey" (https://doi.org/10.1007/978-3-031-39800-1_5).
Usage
sackinI(tree)
Arguments
tree |
A rooted tree in phylo format. |
Value
sackinI
returns the Sackin index of the given tree.
Author(s)
Luise Kuehn
References
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.
Examples
tree <- ape::read.tree(text="((((,),),(,)),(((,),),(,)));")
sackinI(tree)