title: Mapping variable to hexagon size with geom_hex
body: <p>Does anyone know if its possible to map to hexagon size with ggplot?  Size is listed as an argument in the <a href="http://docs.ggplot2.org/current/geom_hex.html" rel="nofollow noreferrer">geom_hex documentation</a>, but there are no examples of size mapping in <a href="http://docs.ggplot2.org/current/stat_binhex.html" rel="nofollow noreferrer">stat_hexbin</a>, so this just seems to relate to bin size.</p>
  
  <p>Take for example:</p>
  
  <pre><code>ggplot(economics, aes(x=uempmed, y=unemploy)) + geom_hex()
  </code></pre>
  
  <p><img src="https://i.stack.imgur.com/GkHWG.png" alt="enter image description here"></p>
  
  <p>But looking for instance at population distribution (below) it might be useful to map binned mean population to hexagon size, but I've not found a formula for this (if one exists).</p>
  
  <pre><code>ggplot(economics, aes(x=uempmed, y=unemploy, col=pop)) + geom_point()
  </code></pre>
  
  <p><img src="https://i.stack.imgur.com/h7i9D.png" alt="enter image description here"></p>
  
  <p>Any ideas?</p>