ment_g <- graph.empty()
ment_g <- ment_g + vertices(all_sn)

for(i in 1:dim(raw_tweets)[1]) {
  ment_name <- mention_ext(raw_tweets$tweet_text[i])

  if(length(ment_name) > 0 ) {

    # Add the edge(s)
    for(j in ment_name) {

      # Check to make sure the vertex exists, if not, add it
      if(!j %in% all_sn) { 
        ment_g <- ment_g + vertices(j)  }
      ment_g <- ment_g + edges(c(raw_tweets$screen_name[i], j))
    }
  }
}

ment_g <- simplify(ment_g)
ment_g <- delete.vertices(ment_g, degree(ment_g) == 0)