title: Order by letters and numbers
body: <p>I have a <code>DF$vector</code> which looks like this:</p>
  
  <pre><code>A10 A50
  C1 C4
  B1
  A7
  C3
  B1 B4
  </code></pre>
  
  <p>I look for a way to order it as follows:</p>
  
  <pre><code>A10 A50
  A7
  B1 B4
  B1
  C1 C4
  C3
  </code></pre>
  
  <p>I tried to use <code>gsub</code> :</p>
  
  <pre><code>vector[order(gsub("([A-Z]+)([0-9]+)", "\\1", vector), 
               as.numeric(gsub("([A-Z]+)([0-9]+)", "\\2", vector)))]
  </code></pre>
  
  <p>But it didnt return what i want. 
  Thank you for any suggestions.</p>