title: How to predict x values from a linear model (lm)
body: <p>I have this data set:</p>
  
  <pre><code>x &lt;- c(0, 40, 80, 120, 160, 200)
  y &lt;- c(6.52, 5.10, 4.43, 3.99, 3.75, 3.60)
  </code></pre>
  
  <p>I calculated a linear model using <code>lm()</code>:</p>
  
  <pre><code>model &lt;- lm(y ~ x)
  </code></pre>
  
  <p>I want know the predicted values of <code>x</code> if I have new <code>y</code> values, e.g. <code>ynew &lt;- c(5.5, 4.5, 3.5)</code>, but if I use the <code>predict()</code> function, it calculates only new <code>y</code> values.</p>
  
  <p>How can I predict new <code>x</code> values if I have new <code>y</code> values?</p>