title: par(mfrow=c(1,2)) not displaying side-by-side densityplots
body: <pre><code>par(mfrow=c(1,2))
  plot(1:12, log = "y")
  plot(1:2, xaxs = "i")
  </code></pre>
  
  <p><img src="https://i.stack.imgur.com/GVVc0.png" alt="enter image description here"></p>
  
  <p>However, when I try to do a side-by-side densityplot the plots get output seperately:</p>
  
  <pre><code># load the stud.recs dataset
  library(UsingR)
  
  par(mfrow=c(1,2))
  densityplot(stud.recs$sat.v)
  densityplot(stud.recs$sat.m)
  </code></pre>
  
  <p>Why is <code>par(mfrow=c(1,2))</code> not working for the density plots?</p>