Question

I want to create a function for Burt’s effective size.
The formula boils down to:

Effective size = n – 2t/n

• where t is the number of ties (not counting ties to ego)
• n is the number of people in the network (not counting ego).

I’m not really sure where to start with writing functions within/for igraph.

Let me know if more detail would be helpful…

Thanks.

Answer 1

First simulate a basic graph:

require(igraph)

alters = 50
ties   = 10
set.seed(12345)
edgelist = rbind(0, 1:alters)
edgelist = cbind(edgelist, replicate(ties, sample(alters, 2)))
g = graph(edgelist, directed=F)

dev.new(width=5, height=5)
plot(g, layout=layout.kamada.kawai)

Then write a simple function to calculate the effective size. (The functions in here that operate on g are all nicely documented in the igraph manual and in various examples around the net.)

EffectiveSize <- function(g, ego=0) {
  n = neighbors(g, ego)
  t = length(E(g)[to(n) & !to(ego)])
  n = length(n)
  n - 2 * t / n
}

> EffectiveSize(g)
[1] 49.6