title: Cannot read property 'pack' of undefined
body: <p>I use d3.js (latest version - v4). In v3 it is work. I have read documantation about layout.pack. Where is my mistake?</p>
  
  <pre><code>var bubble = d3.layout.pack()
      .sort(null)
      .size([diameter, diameter])
      .padding(2);
  </code></pre>