title: non linear regression 'abline'
body: <p>Still quite new to R (and statistics to be honest) and I have currently only used it for simple linear regression models. But now one of my data sets clearly shows a inverted U pattern. I think I have to do a quadratic regression analysis on this data, but I'm not sure how. What I tried so far is: </p>
  
  <pre><code>    independentvar2 &lt;- independentvar^2
      regression &lt;- lm(dependentvar ~ independentvar + independentvar2)
      summary (regression)
      plot (independentvar, dependentvar)
      abline (regression)
  </code></pre>
  
  <p>While this would work for a normal linear regression, it doesn't work for non-linear regressions. Can I even use the lm function since I thought that meant linear model?</p>
  
  <p>Thanks
  Bert</p>