inverse_line_graph#
- inverse_line_graph(G)[source]#
Returns the inverse line graph of graph G.
If H is a graph, and G is the line graph of H, such that G = L(H). Then H is the inverse line graph of G.
Not all graphs are line graphs and these do not have an inverse line graph. In these cases this function raises a NetworkXError.
- Parameters:
- Ggraph
A NetworkX Graph
- Returns:
- Hgraph
The inverse line graph of G.
- Raises:
- NetworkXNotImplemented
If G is directed or a multigraph
- NetworkXError
If G is not a line graph
Notes
This is an implementation of the Roussopoulos algorithm[R90abc5507a69-1]_.
If G consists of multiple components, then the algorithm doesn’t work. You should invert every component separately:
>>> K5 = nx.complete_graph(5) >>> P4 = nx.Graph([("a", "b"), ("b", "c"), ("c", "d")]) >>> G = nx.union(K5, P4) >>> root_graphs = [] >>> for comp in nx.connected_components(G): ... root_graphs.append(nx.inverse_line_graph(G.subgraph(comp))) >>> len(root_graphs) 2
References
[1]Roussopoulos, N.D. , “A max {m, n} algorithm for determining the graph H from its line graph G”, Information Processing Letters 2, (1973), 108–112, ISSN 0020-0190, DOI link