Biclique function

biclique.r

## Lehmann, Schwartz, and Hansen (2008)
## For use with igraph objects
## via http://stackoverflow.com/questions/31024481/detect-bi-cliques-in-r-for-bipartite-graph

library(igraph)

computeBicliques <- function(graph, k, l) {

  vMode1 <- c()
  if (!is.null(V(graph)$type)) {

    vMode1 <- which(!V(graph)$type)
    vMode1 <- intersect(vMode1, which(degree(graph) >= l))
  }

  nb <- get.adjlist(graph)

  bicliques <- list()

  if (length(vMode1) >= k) {

    comb <- combn(vMode1, k)
    i <- 1
    sapply(1:ncol(comb), function(c) {

      commonNeighbours <- c()
      isFirst <- TRUE

      sapply(comb[,c], function(n) {

        if (isFirst) {

          isFirst <<- FALSE
          commonNeighbours <<- nb[[n]]
        } else {

          commonNeighbours <<- intersect(commonNeighbours, nb[[n]])
        }
      })

      if (length(commonNeighbours) >= l) {

        bicliques[[i]] <<- list(m1=comb[,c], m2=commonNeighbours)
      }

      i <<- i + 1
    })
  }
  bicliques
}