title: How can add text to the center of a D3 sunburst diagram
body: <p>I am using the <a href="http://bl.ocks.org/mbostock/4348373" rel="nofollow">zoomable sunburst example </a>but I am struggling trying to add a text to the center of the diagram and still make it zoomable.
  The idea is that the text in the center will change when I click on a certain arc indicating its length. It seems that the properties of the mouseclick and mouseover dissapear.
  This is what I have tried:  </p>
  
  <pre><code>path.append("svg:text")
          .on("click",click)
          .style("font-size","4em")
          .style("font-weight","bold")
          .text(function(d) { return count_function(data); });
  </code></pre>
  
  <p>Can someone help me understand how to display the text in th center of the chart without losing the click functionality?</p>
  
  <p>Maybe an easier approach would be to select the "g" that represents the circular centre and add text to it once the chart was been displayed. I have tried this but I am unable to successfylly select just this element (sorry I am new to D3), so back to square one.</p>