title: Combine a list of matrices to a single matrix by rows
body: <p>Let's say I have a list of matrices (all with the same number of columns). How would I append / combine these matrices by row ('row bind', <code>rbind</code>) to get a single matrix?</p>
  
  <p>Sample:</p>
  
  <pre><code>&gt; matrix(1, nrow=2, ncol=3)
       [,1] [,2] [,3]
   [1,]    1    1    1
   [2,]    1    1    1
  &gt; matrix(2, nrow=3, ncol=3)
       [,1] [,2] [,3]
  [1,]    2    2    2
  [2,]    2    2    2
  [3,]    2    2    2
  &gt; m1 &lt;- matrix(1, nrow=2, ncol=3)
  &gt; m2 &lt;- matrix(2, nrow=3, ncol=3)
  </code></pre>
  
  <p>Now we can have many matrices in a list, let's say we have only two:</p>
  
  <pre><code>l &lt;- list(m1, m2)
  </code></pre>
  
  <p>I would like to achieve something like:</p>
  
  <pre><code>&gt; rbind(m1, m2)
       [,1] [,2] [,3]
  [1,]    1    1    1
  [2,]    1    1    1
  [3,]    2    2    2
  [4,]    2    2    2
  [5,]    2    2    2
  </code></pre>
  
  <p>I can easily do it on 2 matrices but I am not sure how to do it with a list of matrices.</p>