title: combining rows in sequence file
body: <p>I have a data frame, in which each individual has two rows and I want to combine these two row in on row.</p>
  
  <p>Code lines:</p>
  
  <pre><code>dat &lt;- read.table("cbin.csv",sep="\t", row.names=1)
  dat
      V2 V3 V4 V5
  1_1  A  B  C  D
  1_2  a  b  c  d
  2_1  E  F  G  H
  2_2  e  f  g  h
  3_1  J  K  L  M
  3_2  j  k  l  m
  
  d &lt;- apply( dat[ , colnames(dat) ] , 2 , paste , collapse = " " )
  d
     V2            V3            V4            V5 
  "A a E e J j" "B b F f K k" "C c G g L l" "D d H h M m" 
  </code></pre>
  
  <p>But I want to combine each two rows like this</p>
  
  <pre><code>1  A a B b C c D d
  2  E e F f G g H h
  3  I i J j K k L l
  </code></pre>
  
  <p>How can I do this?</p>