title: Extract characters at a set position
body: <p>I am trying to find a function that will extract characters at a certain position within a string. For example, I have a long file name with a date in it, and I want to end up with only the date:</p>
  
  <pre><code>'LT50420331984221PAC00_B7.tif'
  </code></pre>
  
  <p>and I want only the '1984221' portion.
  I've come up with a complicated function, but was wondering if there is a more elegant solution.</p>