title: How do I draw gridlines using abline() that are behind the data?
body: <p>When I draw grid lines on a plot using <code>abline()</code> the grid lines are drawn over the data.  </p>
  
  <p>Is there a way to draw the <code>abline()</code> lines behind the data? I feel this would look better.</p>
  
  <p>Example:</p>
  
  <pre><code>x &lt;- seq(0, 10)
  y &lt;- x
  plot(x, y, col = 'red', type = 'o', lwd = 3, pch = 15)
  abline(h = seq(0, 10, .5), col = 'lightgray', lty = 3)
  abline(v = seq(0, 10, .5), col = 'lightgray', lty = 3)
  </code></pre>
  
  <p>The plot produced has the gray grid lines going over the data (red line). I would like the red line to be on top of the gray lines.</p>