title: How to split rows to a fixed size and apply grep on each row or sublists
body: <p>is there a way to split a data frame row to a fixed size and apply <code>grep</code> on each row?</p>
  
  <p>I found only this function, but it returns a list with many sublist.</p>
  
  <pre><code>split(x, (0:nrow(x) %/% 300))
  </code></pre>
  
  <p>If there is no way, how can I apply the function <code>grep</code> on every sublist? </p>
  
  <p>EDIT:</p>
  
  <p>Small reproducible example:</p>
  
  <pre><code>a=c("cagtcccaaccataacagaagctggcctcctgaagcttacagtcaaaaac")
  b=c("aatgattaaacatccatgcttatgaattccactgcagcctgctataactg")
  c=c("taacaacatttaataatgaaagtaaatctgctacccccattatattttgc")
  
  k=rbind(a,b,c)
  </code></pre>