On 01/03/2013 02:36 PM, jcjveraa wrote: > To illustrate what I'd need: in this graph > https://www.dropbox.com/s/8nlnqcvhb150utt/example_graph-tool.PNG > I for instance want to get all cyclic induced subgraphs with 3 vertices. > The algorithm should return [0,1,4], [0,2,4], [2,3,4] and [3,5,6]. Of > course it's fine if it finds [4,1,0], [1,0,4] and [4,0,1] and suchlike > as well, I can filter easily based on the vertices contained in the > subgraph. > > If I look for a subgraph with 4 vertices, I want 0 hits because > [0,1,2,4] has a chord due to edge [0,4]. > > Any suggestions on a combination of functions to achieve this would be > greatly appreciated :)
This can be done simply as follows, if I understood correctly:
from graph_tool.all import *
g = Graph(directed=False)
g.add_vertex(7)
edges = [(5, 6), (5, 3), (6, 3), (3, 4), (3, 2), (4, 2),
(4, 0), (4, 1), (2, 0), (1, 0)]
for e in edges:
g.add_edge(e[0], e[1])
def get_cycle(n):
u = Graph(directed=False)
u.add_vertex(n)
for i in range(n - 1):
u.add_edge(i, i + 1)
u.add_edge(n - 1, 0)
return u
S = get_cycle(3)
vmaps, emaps = subgraph_isomorphism(S, g)
for vm, em in zip(vmaps, emaps):
vmask, emask = mark_subgraph(g, S, vm, em)
F = Graph(GraphView(g, vfilt=vmask), prune=True)
if isomorphism(F, S):
print("found: ", vm.a)
For this I get:
found: [5 6 3]
found: [5 3 6]
found: [1 4 0]
found: [1 0 4]
found: [6 5 3]
found: [6 3 5]
found: [2 4 3]
found: [2 4 0]
found: [2 3 4]
found: [2 0 4]
found: [4 1 0]
found: [4 2 3]
found: [4 2 0]
found: [4 3 2]
found: [4 0 1]
found: [4 0 2]
found: [3 5 6]
found: [3 6 5]
found: [3 2 4]
found: [3 4 2]
found: [0 1 4]
found: [0 2 4]
found: [0 4 1]
found: [0 4 2]
And indeed, if I make S = get_cycle(4), no induced subgraphs are found.
Does this help?
Cheers,
Tiago
--
Tiago de Paula Peixoto <[email protected]>
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