title: Combine two vectors into one in R
body: <p>I would like to merge two character vectors into one by the following logic: </p>
  
  <pre><code>A &lt;- c("005", "NA", "100", "NA")
  B &lt;- c("005", "NA", "NA", "257")
  
  C &lt;- c("005", "NA", "100", "257") 
  </code></pre>
  
  <p>Let's say I have vector <code>A</code> and <code>B</code> and I want to merge them in such a way that I get vector <code>C</code>, how can I achieve that?</p>