title: what's the absolute shortest d3 area example?
body: <p>I'm really struggling to understand d3's <code>area</code> and <code>stack</code> layout stuff. I tried making what I thought was the smallest example but nothing appears and in fact it prints errors in the console. What am I not getting? Here's the code.</p>
  
  <pre><code>var svg = d3.select("body").append("svg")
      .attr("width", 400)
      .attr("height", 300)
  
  var testData = [
    [ 0, 10],
    [10, 20],
    [20, 30],
    [30, 20],
  ];
  
  svg.selectAll("path.area")
      .data(testData)
    .enter().append("path")
      .style("fill", "#ff0000")
      .attr("d", d3.svg.area());
  </code></pre>