This function groups a set of nodes in according to their maximum depth in the graph. It first inverts the weights
of the graph and then applies the Bellman Ford algorithm to find the shortest path, achieving in this way the longest path.
Usage
graph.levels(g, root = "00")
Arguments
g
an object of class graphNEL
root
name of the root node (def. root="00")
Value
a list of the nodes grouped w.r.t. the distance from the root: the first element of the list corresponds to the root node (level 0),
the second to nodes at maximum distance 1 (level 1), the third to the node at maximum distance 3 (level 2) and so on.