title: Vega Edge bundling (directed) - vary thickness of each edge to show strength of connection
body: <p>I am looking to use an edge bundle visualisation as per:</p>
  <p><a href="https://vega.github.io/editor/#/examples/vega/edge-bundling" rel="nofollow noreferrer">https://vega.github.io/editor/#/examples/vega/edge-bundling</a></p>
  <p>However, in this example, all the directed edges are of uniform thickness.</p>
  <p>Instead, I need to generate edges of varying thickness to illustrate the strength of the relationship between nodes.</p>
  <p>I envisaged passing that thickness into the model such that the edges defined by the JSON at
  <a href="https://github.com/vega/vega-datasets/blob/master/data/flare-dependencies.json" rel="nofollow noreferrer">https://github.com/vega/vega-datasets/blob/master/data/flare-dependencies.json</a></p>
  <p>would be adjusted so an edge currently defined as:</p>
  <pre><code>  {
      &quot;source&quot;: 190,
      &quot;target&quot;: 4
    },
  </code></pre>
  <p>would instead be defined as say:</p>
  <pre><code>  {
      &quot;source&quot;: 190,
      &quot;target&quot;: 4,
      &quot;edgeWeight&quot;: 23
    },
  </code></pre>
  <p>Is this possible? I did try experimenting by passing two simplified JSON datasets using value but couldn't figure out how to feed in that &quot;edgeWeight&quot; variable to the line definition in  'marks'.</p>
  <p>Do you know how I might do that?</p>
  <p>Regards,</p>
  <p>Simon</p>