Note

This documents the development version of NetworkX. Documentation for the current release can be found here.

networkx.algorithms.core.k_core

k_core(G, k=None, core_number=None)[source]

Returns the k-core of G.

A k-core is a maximal subgraph that contains nodes of degree k or more.

Parameters
GNetworkX graph

A graph or directed graph

kint, optional

The order of the core. If not specified return the main core.

core_numberdictionary, optional

Precomputed core numbers for the graph G.

Returns
GNetworkX graph

The k-core subgraph

Raises
NetworkXError

The k-core is not defined for graphs with self loops or parallel edges.

See also

core_number

Notes

The main core is the core with the largest degree.

Not implemented for graphs with parallel edges or self loops.

For directed graphs the node degree is defined to be the in-degree + out-degree.

Graph, node, and edge attributes are copied to the subgraph.

References

1

An O(m) Algorithm for Cores Decomposition of Networks Vladimir Batagelj and Matjaz Zaversnik, 2003. https://arxiv.org/abs/cs.DS/0310049