title: R will plot but won't draw abline
body: <pre><code>&gt; head(returnee)
  [1]  1.3936536 -0.6730667  2.3584725  2.3477308  3.2841443  1.3168157
  &gt; head(vixee)
  [1] 14.75 15.45 17.59 17.74 17.75 18.35
  &gt; class(returnee)
  [1] "numeric"
  &gt; class(vixee)
  [1] "numeric"
  &gt; plot(returnee, vixee)
  &gt; abline(lm(returnee ~ vixee))
  </code></pre>
  
  <p>When I run this, it gives the plot, but there is no abline.  Any suggestions?  Thanks.</p>