title: Combining/Merging two graphs in igraph
body: <p>I created the following two graphs using igraph: </p>
  
  <pre><code>t1terms &lt;- c("fire",
              "people",
              "residents",
              "victims", 
              "affected", 
              "please",
              "can",
              "london",
              "support",
              "survivors")
  
  t1labels &lt;- as.vector(t1terms)
  
  g&lt;-graph.full(n=10, directed = FALSE, loops = FALSE) %&gt;%
    set_vertex_attr("label", value = t1labels)
  
  
  t2terms &lt;- c("fire",
               "victims",
               "says",
               "people",
               "cladding",
               "police",
               "may",
               "will",
               "dead",
               "theresa")
  
  t2labels &lt;- as.vector(t2terms)
  
  g1&lt;-graph.full(n=10, directed = FALSE, loops = FALSE) %&gt;%
    set_vertex_attr("label", value = t2labels)
  </code></pre>
  
  <p>I can't figure out how to merge the two graphs without duplicating common nodes. I really appreciate some help. I tried 'graph.union', but it didn't work. </p>
  
  <p>Thank you,</p>
  
  <p>Chamil</p>