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## Re: [igraph] cohesive.blocks()

 From: Gabor Csardi Subject: Re: [igraph] cohesive.blocks() Date: Mon, 28 Apr 2008 16:30:35 +0200 User-agent: Mutt/1.5.13 (2006-08-11)

```Hello,

to be honest, i don't really understand the question.
In your graph (==block 1, cohesion 1) the algorithm finds
two sub-blocks (block 2, cohesion 2, and block 3, cohesion 2).
In block 2 there is a (more) cohesive sub-block, this
will be block 4, it has cohesion 5. Within block 3, there is
a 3-cohesive block, this will be block 5.

In the last case, the remainder of block 3, i.e. the vertices
not in block 5 (vertices 8, 9, 10, 11, 12, 14, 15) do not
constitute a cohesive block, that's why they are not included in
the result.

If in a B cohesive block there is a sub-block C with higher
cohesion value, that does not mean that B-C (the remainder)
has a higher cohesion value (than the original B block) as well.

Gabor.

On Mon, Apr 28, 2008 at 05:54:20PM +0900, MATSUDA, Noriyuki wrote:
> Hello:
>
>    I have some difficulty in relating the performance of
> cohesive.blocks() to the original paper by Moody and White (2003),
> particularly the concepts of components and blocks.  Here is my trial
> on Figures 2 and 3 in the paper:
>   It separates terminal (bottom) blocks 4 and 5, leaving  {17-23}
> unextracted.   Do we need to identify {17-23} by taking the
> difference between blocks 2 and 4?  If so, it would require a lot of
> care even with a graph of medium size.  Or have I made errors in
> specifying edges?
>   Thanks in advance for helping me out.
>
[...]

--
Csardi Gabor <address@hidden>    UNIL DGM

```

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