let centralityDegree graph fd =
let n = float_of_int (G.nb_vertex graph) in
let cd v = (float_of_int v) /. (n -. 1.0) in
let m =
G.fold_vertex (fun v max ->
let s = (List.length (fd graph v)) in
let m = cd s in
if m > max then m else max
) graph 0.0
in
let c =
G.fold_vertex (fun v sum ->
let s = (List.length (fd graph v)) in
(sum +. (m -. (cd s)))
) graph 0.0
in c /. (n -. 2.0)