title: Manipulating a Data frame in R
body: <p>I am new in R. I have data frame </p>
  
  <pre><code>A 5 8 9 6
  B 8 2 3 6
  C 1 8 9 5
  </code></pre>
  
  <p>I want to make </p>
  
  <pre><code>A 5
  A 8
  A 9
  A 6
  B 8
  B 2
  B 3
  B 6
  C 1
  C 8
  C 9
  C 5
  </code></pre>
  
  <p>I have a big data file </p>