title: NVD3 time formatting , line with focus chart
body: <p>I'm using a fairly simple example of nvd3 line with focus chart. <code>myData</code> returns a JSON object from my php file of which the x-cordinates are numbers from 0-23. I would like to know how to format the x-axis in hours format. </p>
  
  <pre><code> d3.json('get_data.php', function (error, myData) {
    // Renders a line chart
    (function () {
        nv.addGraph(function () {  
            var chart = nv.models.lineWithFocusChart();
            chart.xAxis                
              .tickFormat(d3.format(''));
            chart.yAxis
              .tickFormat(d3.format(''));
            chart.y2Axis
              .tickFormat(d3.format(''));
  
            d3.select("#chart svg")               
                .datum(myData)
                .transition().duration(500)
                .call(chart);    //Define transition and pass the d3.selection to our lineChart.
  
  
            nv.utils.windowResize(chart.update);
  
            return chart;   //Must return the enclosed chart variable so the global rendering queue can store it.
            //});
        });
    })();  });
  </code></pre>
  
  <p>Here is the sample json data in <code>myData</code>. Do I need to manipulate it in anyway?</p>
  
  <p><code>[{
      "key": "data",
      "values": [
        {
          "x": 0,
          "y": 408175
        },
        {
          "x": 1,
          "y": 428739
        },
        {
          "x": 2,
          "y": 422141
        },
        {
          "x": 3,
          "y": 439864
        },
        {
          "x": 4,
          "y": 441409
        }
      ]
    }]</code>
  Any help is appreciated.</p>