title: How to get the value of each cell in a cell array
body: <p>I wanna ask a question about cell array. Suppose I have a cell array<br>
      <code>C={[2 1], [3 5], [15 6]};</code><br>
  I'd like to get all first value of each cell, which are [2, 3 , 15]
  however, when I type<br>
  <code>C{:}(1);</code><br>
  or<br>
  <code>C(:)(1);</code>
  There would be some mistakes.
  So what is the simplist way to get those numbers.</p>