[igraph] triad census

[Tadaishi Yatabe-Rodriguez]

Hi all,

I'm trying to calculate transitivity of the form B <- A -> C, where also B->C in a directed graph. For this I counted all the neighbors looping over each vertex using the function neighbors(graph[i], mode='out'). Then I counted the number of neighbors using the function length. Finally I get the number of possible triplets for each vertex using combinatorial, i.e. choose(number.neihgbors, 2) and I got the number of triplets of the form  B <- A -> C for each vertex. When I added them all and then compare with the results from triad census for the same kind of triplets results didn't match. Any idea why? Here's the code

##Successors of A

Successor=list()

for (i in 1:vcount(el.13)){

  Successor[[i]] <- neighbors(el.13, v=V(el.13)[i], mode = "out")

}

### Clustering of the form B <- A -> C, where also B->C

n.succ <- sapply(Successor, FUN=length)

trip <- choose(n.succ, 2)

triplets <- sum(trip)

Thanks!

--

Tadaishi Yatabe

DVM, MPVM, PhD (C)

Center for Animal Disease Modeling and Surveillance (CADMS)

Department of Medicine and Epidemiology

School of Veterinary Medicine

University of California Davis