title: Displaying date in nvd3 multichart
body: <p>I'm trying to display dates on a nvd3 Graph. I've done this successfully using the lineChart model but am struggling with the multiChart model.</p>
  
  <p>The graph displays correctly, but I just can get the x axis labels to work. From what I can see this is because the value of d passed tickFormat is NaN, I'm not sure why.</p>
  
  <pre><code>chart.xAxis.tickFormat(d)
  </code></pre>
  
  <p>This means I can't get the value to create a d3.time.format from.</p>
  
  <p>However after the chart is drawn the value of d is what I'd expect ( it's the return value of the chart.x function ).</p>
  
  <pre><code>var chart = nv.models.multiChart()
  .x(function(data,increment){
      return data.x
  });
  </code></pre>
  
  <p>I'm  a little bit over my head with this, trying to understand the nv source code, but how this all hangs together isn't intuitive to me yet!</p>
  
  <p>Any help advice would as always be greatly appreciated.</p>
  
  <p>Thanks</p>
  
  <p>Alan</p>