title: dc.js dimension group ordering
body: <p>I am trying to render a dc.js barChart where my y-axis is percentage 0-100% and my x-axis are numbers, however I want to order the x-axis by date.</p>
  
  <p>My data looks like this:</p>
  
  <pre><code>date,trend,percent
  01/01/2014 13:00,238,53.6
  01/01/2014 13:15,239,64.2
  01/01/2014 13:30,219,43.1
  01/01/2014 13:45,219.2,43.1
  01/01/2014 14:00,237.4,50.6
  ...
  </code></pre>
  
  <p>I am adding the data to crossfilter</p>
  
  <pre><code>data.forEach(function (d) { d.date = parseDate(d.date); });
  
  var ndx = crossfilter(data);
  
  var trendDimension = ndx.dimension(function (d) { return d.trend; });
  var trendGroup = trendDimension.group().reduce(
    function (p, v) {
      p.time = v.date.getTime();
      p.trend = +v.trend;
      p.percent = +v.percent;
      return p;
    },
    ...
  ).order(function (p) { return p.time; }); // ??? order by time rather than trend
  </code></pre>
  
  <p>When I graph the dimension and group, my x-axis is sorted by trend as my x domain looks like:</p>
  
  <pre><code>var minTrend = trendDimension.bottom(1)[0].trend;
  var maxTrend = trendDimension.top(1)[0].trend;
  
  ...
  chart.x(d3.scale.linear().domain([minTrend, maxTrend]);
  ...
  chart.render();
  </code></pre>
  
  <p>Everything plots, however the bars a sorted in order of trend and I would like them sorted in order of date/time.</p>
  
  <p>Is this possible?</p>
  
  <p><strong>EDIT</strong></p>
  
  <p>I also tried:</p>
  
  <pre><code>chart.ordering(function (d) { return d.value.time; });
  </code></pre>
  
  <p>but that does not seem to have an effect on the ordering...</p>