Connected component as a subgraph

graph-tool
1

Hi
The min_spanning_tree function works only for connected graph. So in ordrer to find a minimum spanning forest of a undirected weighted graph (say G), I need to retrieve the connected components of G. I can do it with the label_components function. The problem I have now is I don't know how to build the subgraph induced by each connected component. Here is the piece of code I am working from :

# ----------------------------
import graph_tool as gt
from graph_tool.topology import min_spanning_tree, label_components
import numpy as np

wedges=[(1, 2, 3.), (0, 2, 6.), (3, 4, 1.)]
g= gt.Graph(directed=False)
weight = g.new_edge_property("double")
g.add_edge_list(np.array(wedges), eprops=[weight])
u, v=label_components(g)
print(u.a)
# ----------------------------

outputting

[0 0 0 1 1]

Can somebody explain how to retrieve the subgraph of g induced by the connected component labeled 0?

Thanks in advance

2

The easiest is to create a graph view:

    sub = GraphView(g, vfilt=u.a == 0) # sub contains only the vertices of
                                         # the component with label 0

Best,
Tiago

3

Thanks Tiago, works perfectly.

Can somebody explain how to retrieve the subgraph of g induced by the connected component labeled 0?

The easiest is to create a graph view:

    sub = GraphView(g, vfilt=u.a == 0) # sub contains only the vertices of
                                         # the component with label 0