title: D3 Hierarchy function not calculating y property
body: <p>I am currently working on a tree chart using d3 and this is my data,</p>
  <pre><code>data = {
    name: 'ROOT',
    id: 'root',
    children: [
        {
            name: 'A',
            id: 'A',
            description: 'This is a tooltip with a long multi line text in it',
            children: [
                {
                    name: 'AA',
                    id: 'AA',
                    description: 'This is a tooltip'
                },
                {
                    name: 'BB',
                    id: 'BB'
                }
            ]
        },
        {
            name: 'B',
            id: 'B',
            children: [
                {
                    name: 'AA',
                    id: 'AA'
                },
                {
                    name: 'BB',
                    id: 'BB'
                },
                {
                    name: 'CC',
                    id: 'CC'
                }
            ]
        }
    ]
  </code></pre>
  <p>};</p>
  <p>When I pass this data to d3.hierarchy() and after consoling the result the y property is not defined. Can you explain why the y property is not calculated. Also the nodes calculated through descendants() also have the y property missing.
  <a href="https://i.stack.imgur.com/RNfez.png" rel="nofollow noreferrer">Result after passing the data to d3.hierarchy()</a></p>
  <p><a href="https://i.stack.imgur.com/VHosi.png" rel="nofollow noreferrer">Result of nodes calculated through descendants()</a></p>