title: Extract data from cell array and include index of cell for identification
body: <p>I have a <code>69x1</code>cell array. Each row contains 3 columns of double but with variable numbers of rows.</p>
  
  <p>In each row there are, for example;</p>
  
  <p>4x3 double 
  13x3 double 
  ... etc.</p>
  
  <p>I extract all the data from the cell array into one matrix using;</p>
  
  <pre><code>result = vertcat(data{:})
  </code></pre>
  
  <p>What I would like to do is to give them an identify based on which cell they are extracted from in the data cell array.  For example, the 4 rows extracted from the 1st row in the data cell array would have 1 in front of them...so i would get something like;</p>
  
  <pre><code>1,x,y,z
  1,x,y,z
  1,x,y,z
  1,x,y,z (as row 1 in data has 4 rows)
  2,x,y,z
  2,x,y,z (for the 13 rows)
  </code></pre>