anchor.diff:      .y0(function(d) { return y(d.low); })
       .y1(function(d) { return y(d.high); });
   
  -var svg = d3.select("body").append("svg")
  +var svg = d3.select("#vis").append("svg")
       .attr("width", width + margin.left + margin.right)
       .attr("height", height + margin.top + margin.bottom)
     .append("g")
  
positive.code:   .attr("height", "50");
  
  
  </script>
negative.code:   
  </div>
  
  <div id="vis"></div>
  
  <div>
    <h2>data.tsv</h2>
    <pre id="display_data"></pre>
  </div>
  
  <%# data_embed takes two arguments, 
      #1: filename in source/data directory
      #2: the name of the javascript variable the data is bound to. %>
  