title: Add fitted quadratic curve
body: <p>I'm trying to add a fitted quadratic curve to a plot.</p>
  
  <pre><code>abline(lm(data~factor+I(factor^2)))
  </code></pre>
  
  <p>The regression which is displayed is linear and not quadratic and I get this message:</p>
  
  <blockquote>
    <p>Message d'avis : In abline(lm(data ~ factor + I(factor^2)), col =
    palette[iteration]) :   utilisation des deux premiers des 3
    coefficients de régression</p>
  </blockquote>
  
  <p>which means: </p>
  
  <blockquote>
    <p>Use of the first 2 of the 3 regression coefficients</p>
  </blockquote>
  
  <p>When running only the <code>lm()</code> function I don't get any messages.</p>
  
  <p>Here is a sample data:</p>
  
  <pre><code>factor &lt;- 1:7
  data &lt;- c(0.1375000,0.2500000,0.3416667,0.4583333,0.7250000,0.9166667,1.0000000)
  </code></pre>