title: d3 brush partially updating axis not circles
body: <p>I have prepared a bubble chart , which you can zoom into using the brush in ther grey area below the scale.Here is the <a href="http://jsfiddle.net/LfBva/9/" rel="nofollow">fiddle</a>. The code below updates the graph . It is updating the ruler but not graph. Can any one point out why?</p>
  
  <pre><code>function brushmove(){
              x_axis.domain(brush.empty() ? x_axis.domain() : brush.extent());
         svg.select('.ruler').call(x_axis_ruler);
  
  
        blue_circle.selectAll('circle').data(dataset)
        .attr('cx', function (d, i) {
              return x_axis(d.waiting_to_be_processed_time);
          })
  
  
      }
  </code></pre>