title: paste two data.table columns
body: <pre><code>dt &lt;- data.table(L=1:5,A=letters[7:11],B=letters[12:16])
     L A B
  1: 1 g l
  2: 2 h m
  3: 3 i n
  4: 4 j o
  5: 5 k p
  </code></pre>
  
  <p>Now I want to paste columns "A" and "B" to get a new one, let's call it "new":</p>
  
  <pre><code>dt2
     L A B new
  1: 1 g l  gl
  2: 2 h m  hm
  3: 3 i n  in
  4: 4 j o  jo
  5: 5 k p  kp
  </code></pre>