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## Re: [igraph] What exactly does igraph_transitivity_undirected() compute

 From: Gábor Csárdi Subject: Re: [igraph] What exactly does igraph_transitivity_undirected() compute for directed graphs? Date: Mon, 7 Dec 2015 12:16:10 +0000

```I am not sure if it is defined. I guess this is just a case when the
behavior is not defined for multi-graphs.

Gabor

On Mon, Dec 7, 2015 at 12:14 PM, Szabolcs Horvát <address@hidden> wrote:
> Thank you for the explanation.
>
> Could you elaborate a bit on how igraph defines the local clustering
> coefficient when multiple (parallel) edges are present?
>
> On 7 December 2015 at 12:56, Gábor Csárdi <address@hidden> wrote:
>> It's because of the multiple edges in the first graph. I.e.:
>>
>>> transitivity(as.undirected(g, mode = "each"),"local")
>> [1] 0.3333333 0.3333333 1.0000000
>>
>> Gabor
>>
>> On Mon, Dec 7, 2015 at 10:05 AM, Szabolcs Horvát <address@hidden> wrote:
>>> Hello,
>>>
>>> What precisely does igraph_transitivity_undirected() compute for
>>> directed graphs?
>>>
>>> The C documentation states that
>>>
>>> "Directed graphs are considered as undirected ones."
>>>
>>> but this is not exactly the case.
>>>
>>> With an example using the R interface (for simplicity),
>>>
>>>> g<-make_graph(c(1,2, 2,1, 2,3, 3,1))
>>>> transitivity(g,"local")
>>> [1] 0.3333333 0.3333333 1.0000000
>>>
>>>> transitivity(as.undirected(g),"local")
>>> [1] 1 1 1
>>>
>>> Can someone clarify what precisely is computed in the directed case?
>>>
>>> Szabolcs
>>>
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>>
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