Description Usage Arguments Value Author(s) References Examples

This function calculates the stairs2 value *st2(T)* for a given rooted
binary tree *T*. It is defined as the mean ratio between the leaf
numbers of the smaller and larger pending subtree over all inner vertices, more precisely

*st2(T)=1/(n-1)*∑_{u in V_in(T)} (n_ua/n_ub)*

in which *V_in(T)* denotes the set of all inner vertices
of *T*, and in which *n_ua >= n_ub* denote the number of leaves
in the two pending subtrees that are
rooted at the direct descendants of *u*. The stairs2 value is an imbalance index.

Special cases: For *n=1*, the function returns *st2(T)=0* and a warning.

1 | ```
stairs2(tree)
``` |

`tree` |
A rooted binary tree in phylo format. |

`stairs2`

returns the stairs2 value of the given tree.

Sophie Kersting

C. Colijn and J. Gardy. Phylogenetic tree shapes resolve disease transmission patterns. Evolution, Medicine, and Public Health, 2014(1):96-108, 2014. ISSN 2050-6201. doi: 10.1093/emph/eou018.

1 2 |

treebalance documentation built on Oct. 17, 2021, 5:06 p.m.

Embedding an R snippet on your website

Add the following code to your website.

For more information on customizing the embed code, read Embedding Snippets.