EdgeAncestry() returns a logical vector stating whether each edge
in turn is a descendant of the specified edge.
Arguments
edge
Integer specifying the number of the edge whose child edges
should be returned.
parent
Integer vector corresponding to the first column of the edge
matrix of a tree of class phylo, i.e.
tree[["edge"]][, 1]
child
Integer vector corresponding to the second column of the edge
matrix of a tree of class phylo, i.e.
tree[["edge"]][, 2].
stopAt
Integer or logical vector specifying the edge(s) at which to
terminate the search; defaults to the edges with the smallest parent,
which will be the root edges if nodes are numbered Cladewise or in
Preorder.