title: C3 js line chart getting error for date
body: <p>I am trying to use c3.js timeseries line chart (URL : <a href="http://c3js.org/samples/timeseries.html" rel="nofollow">http://c3js.org/samples/timeseries.html</a>). The only difference being that I am using the CDN link to the js files instead of downloading them. However I keep getting the following error</p>
  
  <p><strong>Chrome</strong>
  Uncaught Error: x is not defined for id = "date".</p>
  
  <p><strong>Firefox</strong>
  Error: x is not defined for id = "date".</p>
  
  <p>throw new Error('x is not defined for id = "' + id + '".');
              |
  ------------+</p>
  
  <p>The html file is given below</p>
  
  <pre><code>&lt;!DOCTYPE html&gt;
  &lt;html&gt;
  &lt;meta charset="utf-8"&gt;
  &lt;head&gt;
  
  &lt;link rel="stylesheet" type="text/css" href="http://cdnjs.cloudflare.com/ajax/libs/c3/0.4.10/c3.css"/&gt;
  
  &lt;script src="http://d3js.org/d3.v3.min.js"&gt;&lt;/script&gt;
  &lt;script src="http://cdnjs.cloudflare.com/ajax/libs/c3/0.4.10/c3.js"&gt;&lt;/script&gt;
  
  &lt;script&gt;
      var dates = ['20130101', '20130102', '20130103', '20130104', '20130105', '20130106'];
      var sample = [30, 200, 100, 400, 150, 250];
  
      var chart = c3.generate({
          bindto: '#chart',
          data: {
                  x:'Dates',
                  x_format:'%Y%m%d',
          columns: [
          //['Dates'].concat(dates),
          //['Sample'].concat(sample)
                  ['date', '20130101', '20130102', '20130103', '20130104', '20130105', '20130106'],
                  ['sample', 30, 200, 100, 400, 150, 250]
                  ]
          },
          axis: {
                  x: {
                      type : 'timeseries'
                  }
          }
      });
  &lt;/script&gt;
  &lt;/head&gt;
  &lt;body&gt;
      &lt;div id="chart"&gt;&lt;/div&gt;
  &lt;/body&gt;
  &lt;/html&gt;
  </code></pre>
  
  <p>I am not sure why I am getting the date related errors. I tried using actual data values in the C3 arguments as well as passing the data as variables. Any help is highly appreciated</p>