title: R-Duplicate columns in a matrix
body: <p>I have a matrix</p>
  
  <pre><code>1   2
  1   3
  </code></pre>
  
  <p>I want to duplicate each columns three times to create a matrix like this:</p>
  
  <pre><code>1   1   1   2   2   2
  1   1   1   3   3   3
  </code></pre>
  
  <p>I dont think I can use <code>rep</code>. Really appreciate any help</p>