title: NVD3 - uneven ticks when updating data
body: <p>When I update the data in an existing NVD3 chart, the ticks along the x-axis are not rendering at fixed intervals.</p>
  
  <p>I'm creating a <code>multiBarChart</code> with data sourced from <code>d3.json()</code>. The data represents hits over a date range. I have a separate date range picker which updates the chart's data.</p>
  
  <p>I have the following to create the graph (simplified):</p>
  
  <pre><code>initGraph = function(url) {
    d3.json(url, function(data) {
      nv.addGraph(function() {
        chart = nv.models.multiBarChart();
  
        d3.select('#chart svg').datum(data).transition().duration(500).call(chart);
        nv.utils.windowResize(chart.update);
  
        return chart;
      });
    });
  };
  </code></pre>
  
  <p>And the following function to update it, which is invoked in the date picker:</p>
  
  <pre><code>redrawGraph = function(url) {
    d3.json(url, function(data) {
  
      d3.select('#chart svg').datum(data).transition().duration(500).call(chart);
      nv.utils.windowResize(chart.update);
    });
  };
  </code></pre>
  
  <p>Everything seems fine, however occasionally the tick spacing ends up inconsistent:</p>
  
  <p><img src="https://i.stack.imgur.com/KStcK.png" alt="Wonky ticks"></p>
  
  <p>This only occurs when updating an existing chart.</p>
  
  <p>I've spent quite some time verifying that the data is correct - that the x values are incrementing by fixed values - so I can only think that I'm missing something when redrawing the chart. </p>