Rightmost and leftmost extent of a node in a tree sequence

[hyanwong]

I want to get the span of every node in a tree sequence. As long as I don't mind only looking for nodes which are parents, I reckon the following should do it. It's a bit cryptic, but very fast, as the edges are in the right order already. Possibly a useful recipe?

import numpy as np
import tskit

ts = tskit.load("my.trees")

changed_indexes = np.where(np.diff(np.insert(ts.tables.edges.parent, 0, -1)))[0]
leftmost = np.minimum.reduceat(ts.tables.edges.left, changed_indexes)
rightmost = np.maximum.reduceat(ts.tables.edges.right, changed_indexes)
parent = ts.tables.edges.parent[changed_indexes]

for l, r, p in zip(leftmost, rightmost, parent):
   print(f"Node {p} extends as a parent from {l} to {r}")