[igraph] Betweenness centrality issue

[Antoniazzi Marco]

Hi all,

I have two matrices which look as following:

Matrix A: 14*14 with weighted edges.

Matrix B: 14*14 where I changed all the weighted edges with 1.

I wanted to check whether igraph results are correct but I can't figure out the 
explanations to the following problem:

GraphA <- graph.adjacency(MatrixA, mode=c("directed"),weighted = NULL )   
Betweenness <- betweenness ( GraphA, directed = TRUE,
                            weights = NULL, normalized=TRUE) 

GraphB <- graph.adjacency(MatrixB, mode=c("directed"), weighted= NULL) 
BetweennessN <- betweenness ( GraphB, directed = TRUE,
                              weights = NULL, normalized=TRUE) 

from which I should get exactly the same results as I specify weighted=NULL but 
indeed the results are different one from the other.
I have tried to remove 'normalized' argument to see whether it is biased but I 
get different results as well...

Any thoughts?

Thank you very much for your help!!
Marko