How to do a summation in R using igraph package

Question

I am trying to calculate the queue size in a network in R. For that at first I calculate the betweenness centrality of all the nodes in the network which returns a vector. For calculating the queue, I have to do a summation of all the betweenness value for all the nodes and multiply it with some other values which will be constant in my case. I have tried to use a for loop and my code is given below:

between <- betweenness(graphList[[1]], v=V(graphList[[1]]), directed =TRUE, weights = NULL,nobigint = TRUE, normalized = FALSE)
S <- length (between)
A <- 0
for(i in 1:length(S))
{
 A = A + sum (d * l * between [i]/(S - 1 - (d * l * between [i])) )
}

Now the value A returns for only the first value of between, not the entire vector. Is there any other way to calculate this? Can anyone help me on this?

Answer 1

Your problem is that when you call length(S) as your loop variable, you are taking the length of the length of between, ie if length(between) is 29, S = 29 and length(S) is 1. Therefore you only get 1 loop. You can change it to:

for(i in 1:S)....

And it will work.

BUT:

All the calculations you are doing on between are vectorised, so there is no need for a loop:

library(igraph)
set.seed(24)
g <- random.graph.game(10, 3/10)
between <- betweenness(g)
S <- length (between)
A <- 0
d <- 0.5 #not sure what value you had
l <- 0.5 #not sure again
A <- sum((d * l * between /(S - 1 - (d * l * between)) ))
A
[1] 1.219178