title: Getting only matched part of the string in R
body: <p>Is there a function in R that matches regexp and returns only the matched parts? 
  Something like <code>grep -o</code>, so:</p>
  
  <pre><code>&gt; ogrep('.b.',c('abc','1b2b3b4'))
  [[1]]
  [1] abc
  
  [[2]]
  [1] 1b2 3b4
  </code></pre>