title: Arrange plots in a layout which cannot be achieved by 'par(mfrow ='
body: <p>I have three plots which I would to arrange in a single window. I can arrange similar-sized plots on a regular 2*2 grid using <code>par(mfrow = c(2, 2))</code>:</p>
  
  <pre><code>par(mfrow = c(2, 2))
  plot(1:10, main = "plot1")
  plot(10:1, main = "plot2")
  plot(rnorm(10), main = "plot3")
  </code></pre>
  
  <p>However, I want to position "plot1" and "plot2" beside each other on the top row, and "plot3" below them, centered horizontally. How can I achieve this?</p>