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## Re: [igraph] Coreness Out/In meanings

 From: Robin Shields Subject: Re: [igraph] Coreness Out/In meanings Date: Fri, 17 Jun 2011 07:44:29 +0100

Hi Tamas and Gabor -

Thanks, that is a very clear explanation of coreness and how it is calculated. I'll need to think a bit about what this means in terms of my data, but I understand the concept well enough to go ahead. Thanks again.

R

On Thu, Jun 16, 2011 at 7:06 PM, Gábor Csárdi wrote:
Robin,

The k-core of graph is a maximal subgraph in which each vertex has
at least degree k. The coreness of a vertex is k if it belongs to
the k-core but not to the (k+1)-core.

...

mode: The type of the core in directed graphs. Character constant,
possible values: ‘in’: in-cores are computed, ‘out’:
out-cores are computed, ‘all’: the corresponding undirected
graph is considered. This argument is ignored for undirected
graphs.

So in an 'in-core' each vertex has an in-degree of at least k, in an
out-core the same is true for the out-degree, etc. I am not quite sure
how you can interpret an 'in-core' or 'out-core', but it was easy to
calculate them, so I left them in, and kept the default on 'all', i.e.
calculating standard k-cores on the corresponding undirected graph.

Best,
Gabor

On Thu, Jun 16, 2011 at 1:17 PM, Robin Shields <address@hidden> wrote:
> Hello,
>
> Just started using igraph a few days ago and really like it. I'm working
> with directed, valued data (migration between countries), and analysing
> coreness. When I use mode="all" there is very little change at all,but I
> notice very different trends using the coreness mode="out" and mode="in"
> values - could anyone give a common-sense/lay person's interpretation of
> what these measurements mean? Or possibly a good/link reference to follow up
> with? Thanks very much.
>
> Best,
> Robin
>
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>
>

--
Gabor Csardi <address@hidden>     MTA KFKI RMKI

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