Calculates the staircaseness measure.
1  stairs(tree)

tree 
a tree of class 
Two numbers corresponding to the two staircaseness measures for a tree. Defined in Norstrom et al., Evolutionary Bioinformatics online, 8:261 (2012) doi: 10.4137/EBO.S9738, these are two related measures:
1: the proportion of subtrees that are imbalanced (i.e. subtrees where the left child has more tip descendants than the right child, or vice versa)
2: the average of all the min(l,r)/max(l,r) values of each subtree, where l and r are the number of tips in the left and right children of a subtree.
Michael Boyd mboyd855@gmail.com
Michelle Kendall michelle.louise.kendall@gmail.com
1 2 3  ## Find the staircaseness measures in a random tree with 20 tips:
stairs(rtree(20))

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