title: How to merge and unmerge a character vector?
body: <p>I need to keep track of my data through a series of calculations. </p>
  
  <p>i have the following vectors:</p>
  
  <pre><code>start_date &lt;- "2010-11-04"
  end_date &lt;- "2010-11-10"
  </code></pre>
  
  <p>i wish to merge them into a single character vector that looks like this</p>
  
  <pre><code>"2010-11-04 to 2010-11-10"
  </code></pre>
  
  <p>then i would like the inverse:</p>
  
  <p>from: <code>"2010-11-04 to 2010-11-10"</code> back to the original two vectors </p>