title: Concatenate two 3D matrices in each page without loop
body: <p>Suppose two 3D matrices <code>a</code> and <code>b</code>, can these two be concatenated in each page/slice? For example:</p>
  
  <pre><code>a(:,:,1)=
  1 2 3
  
  a(:,:,2)=
  7 8 9
  
  b(:,:,1)=
  4 5 6
  
  b(:,:,2)=
  10 11 12
  </code></pre>
  
  <p>So the output would be</p>
  
  <pre><code>output(:,:,1)=
  1 2 3 4 5 6
  
  output(:,:,2)=
  7 8 9 10 11 12
  </code></pre>
  
  <p>As I understood, <code>cat</code> function will concatenate 3D matrix into 2D matrix, but I wanted to keep the 3D format. Any help is appreciated!</p>