title: Aggregating unique character values per group in R
body: <p>I want to aggregate all the keywords in a specific year by groups.</p>
  
  <p>I have a dataset that looks like this: 
  <a href="https://i.stack.imgur.com/jm8cx.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/jm8cx.png" alt="enter image description here"></a></p>
  
  <p>Primary problem for me is that <em>Words</em> column can vary between 1 and 52! I was thinking of splitting this column in different columns and then use group_by. But now I am not sure how to proceed. </p>