title: Draw to add a polygon on my line graph in R
body: <p>I have made the folowing graph with my data using the <code>overlapPlot()</code> function in R.</p>
  
  <p>I would like to add to shaded areas within the graph showing sunrise and sunset. Sunrise is between 6-7 and sunset between 18-19.</p>
  
  <p>To do this I thought I could use the <code>polygon()</code> function. However I am not sure how to code the polygon function to do this. Any help would be appreciated.</p>
  
  <p><img src="https://i.stack.imgur.com/gkwdh.jpg" alt="enter image description here"></p>