[igraph] Assortative mixing

[Thomas]

Does anyone have any guidance on the interpretation of the assortative  
coefficient (R code copied below)? Can it be assessed for significance  
as Pearson's r can? And if so, is the sample size the number of nodes  
in the network? Newman explains his approach in Column 1, Page 3 here: http://arxiv.org/pdf/cond-mat/0209450v2 
 but I couldn't follow it.

Thank you!

Thomas

#Code copied from: http://igraph.wikidot.com/r-recipes
#Assortativity coefficient in R

assortativity <- function(graph){
    deg <- degree(graph)
    deg.sq <- deg^2
    m <- ecount(graph)
    num1 <- 0; num2 <- 0; den <- 0
    edges <- get.edgelist(graph, names=FALSE)+1

    num1 <- sum(deg[edges[,1]] * deg[edges[,2]]) / m
    num2 <- (sum(deg[edges[,1]] + deg[edges[,2]]) / (2 * m))^2
    den <- sum(deg.sq[edges[,1]] + deg.sq[edges[,2]]) / (2 * m)

    return((num1-num2)/(den-num2))
    }