title: How to create relative mark positions in Vega LIte
body: <p>I have a pie chart with width &amp; height set to &quot;container&quot;. I would like to label each slice of the pie. Therefore I included a layer and it creates the correct text. However, I don't know how to implement a relative radius size. How would you go about it?</p>
  <p>With an absolute radius (e.g. 30) it works, but I need a relative position.</p>
  <pre><code>`&quot;layer&quot;: [{&quot;mark&quot;: {&quot;type&quot;: &quot;arc&quot;}},
  {&quot;mark&quot;: {&quot;type&quot;: &quot;text&quot;, &quot;radius&quot;:30},
  &quot;encoding&quot;: {&quot;text&quot;: {&quot;field&quot;: &quot;*&quot;, &quot;type&quot;: &quot;nominal&quot;}}
  }]`
  </code></pre>