title: Merging and change the column names of the merged ones
body: <p>How can I merge 2 data frame and then change the column name of the merged ones. See example below.</p>
  
  <pre><code>&gt; DF1
    A    B  C
  1 3  axe aa
  2 6 base bb
  3 9  lol cc
  
  &gt; DF2
    D  E   F
  1 6 ss gun
  2 3 dd run
  3 9 vv fun
  
  &gt; merge(x=DF1,y=DF2, by.x="A",by.y="D",all.x=TRUE)
    A    B  C  E   F
  1 3  axe aa dd run
  2 6 base bb ss gun
  3 9  lol cc vv fun
  </code></pre>
  
  <p>My question is how can I rename the merged ones the E and F into A.E and A.F
  So it should be like this.</p>
  
  <pre><code>      A  B    C   A.E A.F
        3  axe  aa  dd  run
        6  base bb  ss  gun
        9  lol  cc  vv  fun
  </code></pre>