title: NVD3 Stacked Area chart looks weird
body: <p>I've tried using stacked area chart via NVD3 with some real data and it looks strange:
  <img src="https://i.stack.imgur.com/SZYBO.png" alt="Stacked Area Chart using NVD3"></p>
  
  <p>I guess something's wrong with the data or data accessor function but I can't figure out what exactly. </p>
  
  <pre><code>  var chart = nv.models.stackedAreaChart()
              .x(function(d) { if (typeof d !== "undefined" &amp;&amp; d !== null) return d[0] })
              .y(function(d) { if (typeof d !== "undefined" &amp;&amp; d !== null) return d[1] })
              .clipEdge(true)
              .useInteractiveGuideline(true)
              ;
  </code></pre>
  
  <p>Also I've noticed that it doesn't work at all if "values" array has different length across different data objects. Is it NVD3's restriction or something?</p>
  
  <p><a href="http://jsfiddle.net/y5Xb9/" rel="nofollow noreferrer">My fiddle</a></p>