title: Joining the data in two columns into one column in R
body: <p>I have two columns in a dataset after merging two seperate datasets. I would like to merge these columns into one column, BNR.x.<br /><br />
  For the cases listed below my prefered outcomes would be:<br />
  1. Nothing. BNR.x has data, that's fine.<br />
  2. Nothing. Data in both colums is the same, that's fine.<br />
  3. Data from BNR.y is copied to BNR.x<br />
  4. Nothing. Same as 2.<br />
  5. Data in colums is different. Preferably i'd get an extra column with a 1 of FALSE as warning in this row.<br />
  6. No Data. Preferably i'd get a warning here aswell to notify me that i dont have any data for this item.<br /></p>
  
  <pre><code>+----+-------+-------+
  | ID | BNR.x | BNR.y |
  +----+-------+-------+
  |  1 | 123   | NA    |
  |  2 | 234   | 234   |
  |  3 | NA    | 345   |
  |  4 | 456   | 456   |
  |  5 | 678   | 677   |
  |  6 | NA    | NA    |
  +----+-------+-------+
  </code></pre>
  
  <p>Is there a method or package that will do this for me?</p>