title: How to Merge two columns into one in R
body: <p>I have the two columns and I am trying to merge the two columns into one.</p>
  <pre><code>library(tibble)
  a &lt;- tribble(
      ~Life_Expectancy_At_Birth_1960, ~Life_Expectancy_At_Birth_2013,
      65.5693658536586,                75.3286585365854,
      32.328512195122,                 60.0282682926829,
      32.9848292682927,                51.8661707317073,
      62.2543658536585,                77.537243902439,
      52.2432195121951,                77.1956341463415,
  )
  
  </code></pre>
  <p>The result I want is:</p>
  <pre><code>    Life_Expectancy
      65.5693658536586 
      75.3286585365854   
      32.328512195122  
      60.0282682926829  
      32.9848292682927    
      51.8661707317073 
      62.2543658536585  
      77.537243902439  
      52.2432195121951  
      77.1956341463415
  
  </code></pre>
  <p>and so on</p>
  <p>Any help would be great. Thank you!</p>