title: ggtree change radius scale
body: <p>I am trying to create a phylogenetic tree with ggtree. I am having trouble resizing the centre of the tree so that the symbols on the edge representing my sequences are not overlapping and increasing the radius so that the branch lengths are not as long. Any advice or tips on how to do this would be much appreciated.
  Thanks in advance!</p>
  
  <p>I am using the following script to create the tree...</p>
  
  <pre><code>ggtree(PhyMLAATree, layout = "circular") + 
      geom_tippoint(aes(x=x+.01), shape=Shape, fill=Fill, size=3)
  </code></pre>
  
  <p>These two images show what I am creating and what I am trying to create.
  Tree comes out looking as follows:
  <a href="https://i.stack.imgur.com/X0Uc6.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/X0Uc6.png" alt="This is how the output looks"></a></p>
  
  <p>Would like the final tree to look more like this with a much bigger centre:
  <a href="https://i.stack.imgur.com/WysHn.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/WysHn.png" alt="This is how I would like the tree to look"></a></p>
  
  <p>I have tried allocating a device with more space, but I get the same proportions on the tree (quartz(width=12, height=12)</p>