title: scale.linear() is returning NaN
body: <p>Im running a simple bar chart using d3.scale.linear() and hardcoding he domain range for this example</p>
  
  <p>I can see in firebug that when aplying attr of width to my div, w_bar appears to be NaN.</p>
  
  <p>Why is that?</p>
  
  <pre><code>var w_bar = d3.scale.linear()
      .domain([0, 107525233]) //harcoded
      .range(["0px", "290px"]);
  
  var theList = d3.select("#list").selectAll("div")
      .data(myJSON);
  
  theList.enter().append("div")
      .text(function (d) { return d.v; })
      .transition()
      .duration(1000)
      .attr("width", w_bar); // Why NaN?
  
  theList.exit()
      .remove();
  </code></pre>
  
  <p>Here's the jsfiddle:
  <a href="http://jsfiddle.net/NAhD9/3/" rel="nofollow">http://jsfiddle.net/NAhD9/5/</a></p>