title: Legend in R pch not filled
body: <p>Trying to plot a legend using pch, it is my understanding that these should be filled, but dont appear to be so. Is this a problem with windows graphics?</p>
  
  <pre><code>legend(36, 79,
      legend = c(expression("a"["a"]), expression("b"["b"]), expression("c"["c"])),
      pch = c(21, 8, 24), col = c(grey(0.1), grey(0.3), grey(0.5)),
      cex = 1.3, bty = "n"
  )
  </code></pre>
  
  <p><a href="https://i.stack.imgur.com/AgdI7.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/AgdI7.png" alt="enter image description here"></a>
  would normally not be an issued but this is for a paper to be submitted and the legend and graphics in plot should match
  thanks!</p>