title: stripping out all characters from a string, leaving numbers
body: <p>Hay, i have a string like this:</p>
  
  <pre><code>v8gn5.8gnr4nggb58gng.g95h58g.n48fn49t.t8t8t57
  </code></pre>
  
  <p>I want to strip out all the characters leaving just numbers (and .s)</p>
  
  <p>Any ideas how to do this? Is there a function prebuilt?</p>
  
  <p>thanks</p>