title: Replace the values
body: <p>I have two variables transID and transid</p>
  
  <pre><code>transID        transid
  fsdfsdgls         NA
  dfdsfgdsgs     mksdjfl
  werwer         fgsdsdg
  xcvcxvx           NA
  </code></pre>
  
  <p>I want the output like</p>
  
  <pre><code>transID         transid
  fsdfsdgls          NA 
  mksdjfl         mksdjfl 
  fgsdsdg         fgsdsdg
  xcvcxvx           NA
  </code></pre>
  
  <p>I want to replace the value in transID with transid when it is not NA</p>