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| """Attracting components.""" | |
| import networkx as nx | |
| from networkx.utils.decorators import not_implemented_for | |
| __all__ = [ | |
| "number_attracting_components", | |
| "attracting_components", | |
| "is_attracting_component", | |
| ] | |
| def attracting_components(G): | |
| """Generates the attracting components in `G`. | |
| An attracting component in a directed graph `G` is a strongly connected | |
| component with the property that a random walker on the graph will never | |
| leave the component, once it enters the component. | |
| The nodes in attracting components can also be thought of as recurrent | |
| nodes. If a random walker enters the attractor containing the node, then | |
| the node will be visited infinitely often. | |
| To obtain induced subgraphs on each component use: | |
| ``(G.subgraph(c).copy() for c in attracting_components(G))`` | |
| Parameters | |
| ---------- | |
| G : DiGraph, MultiDiGraph | |
| The graph to be analyzed. | |
| Returns | |
| ------- | |
| attractors : generator of sets | |
| A generator of sets of nodes, one for each attracting component of G. | |
| Raises | |
| ------ | |
| NetworkXNotImplemented | |
| If the input graph is undirected. | |
| See Also | |
| -------- | |
| number_attracting_components | |
| is_attracting_component | |
| """ | |
| scc = list(nx.strongly_connected_components(G)) | |
| cG = nx.condensation(G, scc) | |
| for n in cG: | |
| if cG.out_degree(n) == 0: | |
| yield scc[n] | |
| def number_attracting_components(G): | |
| """Returns the number of attracting components in `G`. | |
| Parameters | |
| ---------- | |
| G : DiGraph, MultiDiGraph | |
| The graph to be analyzed. | |
| Returns | |
| ------- | |
| n : int | |
| The number of attracting components in G. | |
| Raises | |
| ------ | |
| NetworkXNotImplemented | |
| If the input graph is undirected. | |
| See Also | |
| -------- | |
| attracting_components | |
| is_attracting_component | |
| """ | |
| return sum(1 for ac in attracting_components(G)) | |
| def is_attracting_component(G): | |
| """Returns True if `G` consists of a single attracting component. | |
| Parameters | |
| ---------- | |
| G : DiGraph, MultiDiGraph | |
| The graph to be analyzed. | |
| Returns | |
| ------- | |
| attracting : bool | |
| True if `G` has a single attracting component. Otherwise, False. | |
| Raises | |
| ------ | |
| NetworkXNotImplemented | |
| If the input graph is undirected. | |
| See Also | |
| -------- | |
| attracting_components | |
| number_attracting_components | |
| """ | |
| ac = list(attracting_components(G)) | |
| if len(ac) == 1: | |
| return len(ac[0]) == len(G) | |
| return False | |