Re: [igraph] betweenness centrality -- negative and floating values?

[Tamas Nepusz]

> some example values for the betweenness centrality
> 58743768046350440071168.000000 or -466347974268824518656.000000
>
> Does anyone think these values are correct?
They definitely aren't, considering that there are only at most ~10^8  
geodesics in a network with 10^4 nodes. I don't know what's going on  
here; I'm not sure if "%lf" as a format string is right, I might try  
it with "%f" only.

> Furthermore, I have got some floating numbers for the betweenness.
> This is also interesting for me because BC of a vertex "is the number
> of geodesics going through it". This means BC should be integer
> values, doesn't it?
Not necessarily; suppose that there are two shortest paths from vertex  
A to vertex B - they are equal and minimal in length but they are not  
exactly the same. In this case, both paths count only with a weight of  
0.5. In general, if there are k different shortest paths between two  
given vertices, they all count with a weight of 1/k

--
Tamas