title: Color gradient in d3 tree map based of another value
body: <p>I am trying to see if a treemap chart can be done using d3 where the size of the box is based on value a and the color for that box is based on value b. I see this example <a href="https://observablehq.com/@d3/treemap" rel="nofollow noreferrer">https://observablehq.com/@d3/treemap</a></p>
  
  <p>But any examples of using two values would be appreciated. Thank you</p>