component
==========

>>> import networkx as NX
>>> from networkx.operators import convert_node_labels_to_integers as cnlti
>>> G=cnlti(NX.grid_2d_graph(4,4),first_label=1,ordering="sorted")

    .. image:: paths_G.png

>>> H=NX.cycle_graph(7)
>>> DH=NX.cycle_graph(7,create_using=NX.DiGraph())


Connected components
--------------------

>>> G1=cnlti(NX.grid_2d_graph(2,2),first_label=0,ordering="sorted")
>>> G2=cnlti(NX.lollipop_graph(3,3),first_label=4,ordering="sorted")
>>> G3=cnlti(NX.house_graph(),first_label=10,ordering="sorted")
>>> DG=NX.DiGraph()
>>> DG.add_edges_from([(1,2),(1,3),(2,3)])
>>> G=NX.union(G1,G2)
>>> G=NX.union(G,G3)
>>> sorted(NX.connected_components(G))
[[0, 1, 2, 3], [4, 5, 6, 7, 8, 9], [10, 11, 12, 13, 14]]
>>> NX.number_connected_components(G)
3


>>> G=cnlti(NX.grid_2d_graph(4,4),first_label=1)

    .. image:: paths_G.png


>>> NX.number_connected_components(G)
1

>>> sorted(NX.connected_components(G)[0])
[1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16]

>>> sorted(NX.node_connected_component(G,1))
[1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16]

>>> H=NX.connected_component_subgraphs(G)[0]
>>> sorted(H.nodes())
[1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16]

>>> NX.is_connected(G)
True
>>> G.add_edge('A','B')
>>> NX.is_connected(G)
False

>>> NX.connected_components(DG)
Traceback (most recent call last):
...
NetworkXError: Not allowed for directed graph G.
              Use UG=G.to_undirected() to create an undirected graph.

>>> NX.number_connected_components(DG)
Traceback (most recent call last):
...
NetworkXError: Not allowed for directed graph G.
              Use UG=G.to_undirected() to create an undirected graph.

>>> NX.connected_component_subgraphs(DG)
Traceback (most recent call last):
...
NetworkXError: Not allowed for directed graph G.
              Use UG=G.to_undirected() to create an undirected graph.

>>> NX.node_connected_component(DG,1)
Traceback (most recent call last):
...
NetworkXError: Not allowed for directed graph G.
              Use UG=G.to_undirected() to create an undirected graph.


>>> NX.is_connected(DG)
Traceback (most recent call last):
...
NetworkXError: Not allowed for directed graph G.
              Use UG=G.to_undirected() to create an undirected graph.