title: R - Create a network from a matrix
body: <p>I have a dataset similar to this:</p>
  <pre><code>Abruzzo&lt;- c(1,0.76,0.8,0.90)
  Campania&lt;- c(0.76,1,0.62,0.69)
  Calabria &lt;- c(0.80,0.62,1,0.85)
  Puglia &lt;- c(0.90,0.69,0.85,1)
  X &lt;-data.frame(Abruzzo,Campania,Calabria,Puglia)
  row.names(X)&lt;- c ('Abruzzo','Campania', 'Calabria', 'Puglia')
  </code></pre>
  <p>This matrix contains cosine similarity values.
  I would like to create a network (with igraph) where the 4 nodes (Abruzzo, Campania, Calabria, Puglia) are all interconnected, and the size of the link depends on the corresponding value of the matrix.
  Thanks</p>