title: How can I mirror a matrix about one of its dimensions?
body: <p>I am using Eigen, but since eigen uses basic maths operators this is basically just a maths question. Here is the pseudo-code for what I am after:</p>
  
  <pre><code>    [1 2 3]
  A = [4 5 6]
      [7 8 9]
  
              [7 8 9]
  A.flipv() = [4 5 6]
              [1 2 3]
  </code></pre>
  
  <p>How could I achieve something like this in Eigen? (I'm using version 3.2)</p>
  
  <p>EDIT: I think what I want to do here is swap the top rows with the bottom rows (some combination of <code>.topRows()</code>, <code>.bottomRows()</code> and <code>.swap()</code>?)</p>