title: Convert an array of strings to a vector of numbers
body: <p>I have this:  </p>
  
  <pre><code>d = {'2.5', '3.5'};
  d = 
  '2.5'    '3.5'
  </code></pre>
  
  <p>How do I convert it to a vector of numbers?  </p>
  
  <pre><code>d = 2.5   3.5
  </code></pre>