title: Comparing a linear regression with a log-linear regression with R
body: <p>I have a model in R where I have regressed the price of a Honda civic on its mileage:</p>
  <pre><code>civic &lt;- read.csv(&quot;civic.csv&quot;)
  c &lt;- civic
  
  plot (c$Mileage, c$Price,
        xlab = &quot;Mileage&quot;,
        ylab = &quot;Price&quot;)
  
  regrPM1 &lt;- lm(Price~Mileage, data = c)
  
  abline (regrPM1, col=&quot;red&quot;,lwd=3)
  </code></pre>
  <p>This gives me the following:</p>
  <p><img src="https://i.stack.imgur.com/jXvAL.png" alt="Plot1" /></p>
  <p>So far so good. Now I have another model:</p>
  <pre><code>regrPM2 &lt;- lm(log(c$Price)~c$Mileage)
  </code></pre>
  <p>And I want to add the corrosponding regression line into the Plot1 from above.
  When I use the abline command:</p>
  <pre><code>abline(regrPM2, col=&quot;green&quot;, lwd=3)
  </code></pre>
  <p>It results in the following plot:</p>
  <p><img src="https://i.stack.imgur.com/vqanq.png" alt="Plot2" /></p>
  <p>Now this can't be used to compare the two models. I am looking for a way to compare them without using a 'log' scale.
  I think, I could use the curve demand to get better results but that did not worked out yet.</p>
  <p>Thankful for any kind of help!</p>