title: Extract words containing special character in R
body: <p>I want to extract words which have "@" symbol in it and remove all
  the other words. So, my data will look like this: </p>
  
  <pre><code>Author Content 
  Name1  Hi,@tim how are you @Blue. 
  Name2  @xyz, are you ok? 
  Name3  it is good @my @you
  </code></pre>
  
  <p>where author and content are column names.</p>
  
  <p>I want data in below format:</p>
  
  <pre><code>Author Content
  Name1  tim
  Name1  Blue
  Name2  xyz
  Name3  my
  Name3  you
  </code></pre>
  
  <p>So, I only want words which have "@" symbol with it and drop everything else. </p>