title: D3 Force Directed Graph nodes in order
body: <p>I am using the Force Directed Graph to build a kind of flow diagram. It works fine except that the nodes have no specific order. They are random. I would like the graph to follow a hierarchical order.</p>
  
  <pre><code>var force = d3.layout.force()
      .nodes(d3.values(nodes))
      .links(links)
      .size([width, height])
      .linkDistance(90)
      .gravity(0.6)
      .charge(-2000)
      .linkStrength(0.3);
  </code></pre>
  
  <p>I want to give the nodes some (numerical) hierarchy. Not explicitly define their placement.</p>
  
  <p>Any help will be appreciated.</p>