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.

1 2 |

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