title: Update Pattern, exit and remove
body: <p>I have a stackblits <a href="https://stackblitz.com/edit/d3-start-above-zero-erhfjn?embed=1&amp;file=index.js&amp;hideNavigation=1" rel="nofollow noreferrer">here</a>. I'm trying to create a simple example using the D3 update pattern. Clicking the update button randomly selects from the data and updates the graph. This is happening but it's putting the new graph on top of the current graph and not removing current graph.</p>
  
  <p>I'm using <code>exit()</code> <code>remove()</code> but obviously not correctly.</p>