V <- LETTERS[1:4]
  edL1 <- vector("list", length=4)
  names(edL1) <- V
  for(i in 1:4)
     edL1[[i]] <- list(edges=c(2,1,4,3)[i], weights=sqrt(i))
  gR <- graphNEL(nodes=V, edgeL=edL1)
  gX <- addNode("X", gR)
set.seed(123)
g1 <- randomGraph(letters[1:10], 1:4, p=.3)
g2 <- addNode("z", g1, edges=list(c("a", "h", "g")))
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