title: Why are my tooltips in d3 not updating correctly?
body: <p>I'm using this <a href="http://jsfiddle.net/s79Zg/" rel="nofollow">jsfiddle</a>.  All of the tooltips are initially correct when I hover over the bars.  But when I click the weekview button to change the graph the tooltips don't get updated.</p>
  
  <p>I believe the problem is in this section:</p>
  
  <pre><code>layer.enter()
      .append("g")
      .attr("class", "layer");
  
  layer.attr("fill", function (d, i) {
      return color(i);
      })
  .append("svg:title")
  .text(function(d){  
      return d[0].s;
  });
  
  layer.exit()
      .remove();
  </code></pre>
  
  <p>The append text is where I add the tooltips.  I thought the enter and exit would refresh the bars and therefore refresh the tooltips but it isn't doing it correctly.  </p>
  
  <p>How do I update the tooltips when my graph changes?</p>