title: Algorithmically construct block matrices (matlab)
body: <p>Let <code>Matrices = [A B C D]</code> be a set of square matrices. I want to construct</p>
  <pre><code>H = [A B C D;
       B A B C;
       C B A B;
       D C B A]
  </code></pre>
  <p>If all I was interested in was the 4 by 4 case, then this would be enough. However, I want to construct the analogous matrix when <code>Matrices = [A B C D E F]</code> etc. What code could I write to do this?</p>