title: A hack to allow arrows size in R igraph to match edge width
body: <p>Though the manual states that this will be a future feature:</p>
  
  <blockquote>
    <p>arrow.size The size of the arrows. Currently this is a constant, so it
    is the same for every edge. If a vector is submitted then only the
    first element is used, ie. if this is taken from an edge attribute
    then only the attribute of the first edge is used for all arrows. This
    will likely change in the future.</p>
    
    <p>The default value is 1.</p>
  </blockquote>
  
  <p>I was wondering if there was a hack around to allow the arrow size to match the edge width (each edge having its own width).</p>
  
  <pre><code>d &lt;- data.frame(start=c("a","a","b","c"),end=c("b","b","c","b"), size=rnorm(4))
  
  
  graph &lt;- graph.data.frame(d, directed=T)
  
  plot(graph,
       vertex.color="white",
       edge.width=E(graph)$size*20,
       edge.arrow.size=E(graph)$size)
  </code></pre>
  
  <p><img src="https://i.stack.imgur.com/Kj42a.jpg" alt="enter image description here"></p>