title: R, merge multiple rows of text data frame into one cell
body: <p>I have a text data frame that looks like below.</p>
  
  <pre><code>&gt; nrow(gettext.df)
  [1] 3
  
  &gt; gettext.df
   gettext
   1 hello,
   2 Good to hear back from you.
   3 I've currently written an application and I'm happy about it
  </code></pre>
  
  <p>I wanted to merge this text data into one cell (to do sentiment analysis) as below </p>
  
  <pre><code>&gt; gettext.df
    gettext
    1 hello, Good to hear back from you. I've currently written an application and I'm happy about it
  </code></pre>
  
  <p>so I collapsed the cell using below code   </p>
  
  <pre><code>paste(gettext.df, collapse =" ")
  </code></pre>
  
  <p>but it seems like it makes those text data into one chunk (as one word) so I cannot scan the sentence word by word.</p>
  
  <p>Is there any way that I can merge those sentence as a collection of sentences, without transforming  as one big word chunk?</p>