title: how to draw two half circles in ggplot in r
body: <p>How can I make a plot like this with two different-sized half circles (or other shapes such as triangles etc.)?</p>
  
  <p><a href="https://i.stack.imgur.com/mm6v0.png" rel="noreferrer"><img src="https://i.stack.imgur.com/mm6v0.png" alt="enter image description here"></a></p>
  
  <p>I've looked into a few options: Another post suggested using some unicode symbol, that didn't work for me. And if I use a vector image, how can I properly adjust the size parameter so the 2 circles touch each other?</p>
  
  <p>Sample data (I would like to make the size of the two half-circles equal to <code>circle1size</code> and <code>circle2size</code>):  </p>
  
  <pre><code>df = data.frame(circle1size = c(1, 3, 2),
                  circle2size = c(3, 6, 5),
                  middlepointposition = c(1, 2, 3))
  </code></pre>
  
  <p>And ultimately is there a way to position the half-circles at different y-values too, to encode a 3rd dimension, like so?
  <a href="https://i.stack.imgur.com/FNBmv.png" rel="noreferrer"><img src="https://i.stack.imgur.com/FNBmv.png" alt="enter image description here"></a></p>
  
  <p>Any advice is much appreciated.</p>