title: abline() function not working in R 3.2.0
body: <p>While using </p>
  
  <pre><code>attach(mtcars)
  plot(wt,mpg)
  </code></pre>
  
  <p>till here it's working fine but when I am trying to add a line to the graph by the below code :</p>
  
  <pre><code>abline(lm (mpg~ wt))
  </code></pre>
  
  <p>I am getting an error : </p>
  
  <blockquote>
    <p><strong>Error in x * x : non-numeric argument to binary operator.</strong></p>
  </blockquote>