Calculates the stairs2 measure, from the phyloTop package. The stairs2 reflects the imbalance at each node, where it represents the average across measure at each node, the measure being min(l, r) / max(l, r), where l and r reflect the number of tips connected at the left (l) and right (r) daughter.
stairs2(input_obj)
number of stairs
phylo object or ltable
Norström, Melissa M., et al. "Phylotempo: a set of r scripts for assessing and visualizing temporal clustering in genealogies inferred from serially sampled viral sequences." Evolutionary Bioinformatics 8 (2012): EBO-S9738.