title: NaN on Force-Directed Layout Append in D3.js
body: <p>I'm using a force-directed layout in D3 that grabs data from a JSON file and then, when one of the nodes is double-clicked, queries the database to find links to that node and updates the links and nodes arrays attempting to append the new data to the viz. It seems when the nodes are appended without links, they work fine, but the links to the xy coordinates end up being NaN. You can see the effect here, just double-click on one of the nodes:</p>
  
  <p><a href="http://blockses.appspot.com/2432083" rel="nofollow">http://blockses.appspot.com/2432083</a></p>