Hi Tiago,
Thank you for your detailed reply, it cleared things up a lot! I would also
like to thank you for your incredible work on graph-tool, its a great package!
Below is the code i now use to count the triangles -
# number of triangles
gc = global_clustering(tempG)
d = tempG.degree_property_map("total")
num_triangles = gc[0] * (d.a * (d.a - 1) / 2).sum() / 3
My test dataset is the CA-HepPh network from SNAP -
http://snap.stanford.edu/data/ca-HepPh.html
However i am not getting the reported number of triangles for the dataset
which, according to SNAP, is - 3,358,499
However from the above graph-tool code i get - 13,434,795
Do you have any idea what might cause the discrepancy between the ground truth
and the computed result?
Thanks again,
Stephen Bonner
> On 2 Apr 2016, at 15:39, Tiago de Paula Peixoto <[email protected]> wrote:
>
> On 01.04.2016 15:51, Stephen Bonner wrote:
>> Is there a primitive function for counting triangles in graph-tool?
>
> The closest one is global_clustering(), which returns:
>
> 3 x number of triangles / number of connected triples
>
> the denominator is easy to compute from the degrees alone (the number of
> triples a node with degree k participates is simply k(k-1)/2). Hence,
> you can get the number of triangles with:
>
>
> d = g.degree_property_map("out")
> n_t = global_clustering(g)[0] * (d.a * (d.a - 1) / 2) .sum() / 3
>
>> Currently i am explicitly creating a triangle graph and then using the motif
>> function to search for this graph. -
>>
>> triangle = Graph()
>> v1 = triangle.add_vertex()
>> v2 = triangle.add_vertex()
>> v3 = triangle.add_vertex()
>> e = triangle.add_edge(v1, v2)
>> e = triangle.add_edge(v1, v3)
>> e = triangle.add_edge(v3, v2)
>> triangle.set_directed(False)
>>
>> motifsgraph, num_triangles = motifs(tempG, 3, motif_list=[triangle])
>>
>> Just wondering if there is a better way to do this as it is 1) slow and 2)
>> turning up some strange results.
>
> This should work too. What strange results are you seeing?
>
> Best,
> Tiago
>
> --
> Tiago de Paula Peixoto <[email protected]>
>
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