title: D3 v4 .rangeBand() equivalent
body: <p>In D3 version 4.x, <code>d3.scale.ordinal()</code> has been changed to <code>d3.scaleOrdinal</code> and <code>d3.rangeRoundBands</code> has been changed to:</p>
  
  <pre><code>d3.scaleBand()
    .rangeRound([range]);
  </code></pre>
  
  <p>To find the width of a band, what is the equivalent of <code>d3.rangeBand()</code>?</p>