title: Create matrix from vector with all vector elements shifted down 2 steps
body: <p>Say I have</p>
  
  <pre><code>v = rbind(1, 1, 0, 0, 0, 0)
  # &gt; v
  # [,1]
  # [1,]    1
  # [2,]    1
  # [3,]    0
  # [4,]    0
  # [5,]    0
  # [6,]    0
  </code></pre>
  
  <p>How would I get to this?</p>
  
  <pre><code># &gt; m
  #       [,1]  [,2]  [,3]
  # [1,]    1     0     0
  # [2,]    1     0     0
  # [3,]    0     1     0 
  # [4,]    0     1     0
  # [5,]    0     0     1
  # [6,]    0     0     1
  </code></pre>