Why is my c3.js pie graph not rendered?
<p>This is javascript code in html script tags for a pie chart that I have taken directly from the samples on c3.js. It doesn't appear on the page. Why doesn't it work? I don't have much experience in coding and even less in javascript specifically, please help me.</p>

<pre><code>&lt;html&gt;
  &lt;head&gt;
    &lt;link rel="stylesheet" type="text/css" href="/css/c3.css"&gt;
  &lt;/head&gt;
  &lt;body&gt;
    &lt;div id="chart"&gt;&lt;/div&gt;

    &lt;script src="http://d3js.org/d3.v3.min.js" charset="utf-8"&gt;&lt;/script&gt;
    &lt;script src="/js/c3.js"&gt;&lt;/script&gt;
    &lt;script&gt;
      var chart = c3.generate({
        data: {
          columns: [
            ["versicolor", 1.4, 1.5, 1.5, 1.3, 1.5, 1.3, 1.6, 1.0, 1.3, 1.4, 1.0, 1.5,
                           1.0, 1.4, 1.3, 1.4, 1.5, 1.0, 1.5, 1.1, 1.8, 1.3, 1.5, 1.2,
                           1.3, 1.4, 1.4, 1.7, 1.5, 1.0, 1.1, 1.0, 1.2, 1.6, 1.5, 1.6,
                           1.5, 1.3, 1.3, 1.3, 1.2, 1.4, 1.2, 1.0, 1.3, 1.2, 1.3, 1.3,
                           1.1, 1.3],
            ["virginica", 2.5, 1.9, 2.1, 1.8, 2.2, 2.1, 1.7, 1.8, 1.8, 2.5, 2.0, 1.9,
                          2.1, 2.0, 2.4, 2.3, 1.8, 2.2, 2.3, 1.5, 2.3, 2.0, 2.0, 1.8,
                          2.1, 1.8, 1.8, 1.8, 2.1, 1.6, 1.9, 2.0, 2.2, 1.5, 1.4, 2.3,
                          2.4, 1.8, 1.8, 2.1, 2.4, 2.3, 1.9, 2.3, 2.5, 2.3, 1.9, 2.0,
                          2.3, 1.8],
            ["setosa", 30],
          ],
          type : 'pie',
          onmouseover: function (d, i) { console.log("onmouseover", d, i, this); },
          onmouseout: function (d, i) { console.log("onmouseout", d, i, this); },
          onclick: function (d, i) { console.log("onclick", d, i, this); },
        },
        axis: {
          x: {
            label: 'Sepal.Width'
          },
          y: {
            label: 'Petal.Width'
          }
        }
      });

      setTimeout(function () {
        chart.load({
          columns: [
            ["setosa", 130],
          ]
        });
      }, 1000);

      setTimeout(function () {
        chart.unload({
          ids: 'virginica'
        });
      }, 2000);
    &lt;/script&gt;
  &lt;/body&gt;
&lt;/html&gt;
</code></pre>