[igraph] Single mode centralization: closeness

[Simone Gabbriellini]

Hello List,

I am trying to implement single mode closeness centralization. The idea comes 
from:

Borgatti, S. P. and Everett, M. G. (1997). Network Analysis of 2-mode Data. 
Social Networks, 19(3):243–269.

and can be summarized as:

"A single mode centralization measures the extent to which nodes in one vertex 
are central relative only to other nodes in the same vertex set. The nodes in 
the other vertex set are not ignored, however, as they are included in the 
computation of each node's centrality score. It is quite possible for there to 
be two very different structures internal to each mode of the dataset. It could 
happen that in one mode there are a lot of actors with a similar centrality 
score whereas in the other mode there may be a highly central event with very 
peripheral other events. "

In order to produce single mode closeness centralization, I have to produce 
closeness first. Because I need a different normalization than (n-1), what is 
the best way in igraph to just get the inverse of the total geodesic distance 
from a node to all other nodes in the network (and then divide it by a custom 
value for normalization)?

thanks in advance,
Simone