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authorS. Solomon Darnell2025-03-28 21:52:21 -0500
committerS. Solomon Darnell2025-03-28 21:52:21 -0500
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treeee3dc5af3b6313e921cd920906356f5d4febc4ed /.venv/lib/python3.12/site-packages/networkx/algorithms/hierarchy.py
parentcc961e04ba734dd72309fb548a2f97d67d578813 (diff)
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+"""
+Flow Hierarchy.
+"""
+
+import networkx as nx
+
+__all__ = ["flow_hierarchy"]
+
+
+@nx._dispatchable(edge_attrs="weight")
+def flow_hierarchy(G, weight=None):
+ """Returns the flow hierarchy of a directed network.
+
+ Flow hierarchy is defined as the fraction of edges not participating
+ in cycles in a directed graph [1]_.
+
+ Parameters
+ ----------
+ G : DiGraph or MultiDiGraph
+ A directed graph
+
+ weight : string, optional (default=None)
+ Attribute to use for edge weights. If None the weight defaults to 1.
+
+ Returns
+ -------
+ h : float
+ Flow hierarchy value
+
+ Raises
+ ------
+ NetworkXError
+ If `G` is not a directed graph or if `G` has no edges.
+
+ Notes
+ -----
+ The algorithm described in [1]_ computes the flow hierarchy through
+ exponentiation of the adjacency matrix. This function implements an
+ alternative approach that finds strongly connected components.
+ An edge is in a cycle if and only if it is in a strongly connected
+ component, which can be found in $O(m)$ time using Tarjan's algorithm.
+
+ References
+ ----------
+ .. [1] Luo, J.; Magee, C.L. (2011),
+ Detecting evolving patterns of self-organizing networks by flow
+ hierarchy measurement, Complexity, Volume 16 Issue 6 53-61.
+ DOI: 10.1002/cplx.20368
+ http://web.mit.edu/~cmagee/www/documents/28-DetectingEvolvingPatterns_FlowHierarchy.pdf
+ """
+ # corner case: G has no edges
+ if nx.is_empty(G):
+ raise nx.NetworkXError("flow_hierarchy not applicable to empty graphs")
+ if not G.is_directed():
+ raise nx.NetworkXError("G must be a digraph in flow_hierarchy")
+ scc = nx.strongly_connected_components(G)
+ return 1 - sum(G.subgraph(c).size(weight) for c in scc) / G.size(weight)