title: Use group_by to filter specific cases while keeping NAs
body: <p>I want to filter my dataset to keep cases with observations in a specific column. To illustrate: </p>
  
  <pre><code>help &lt;- data.frame(deid = c(5, 5, 5, 5, 5, 12, 12, 12, 12, 17, 17, 17),
                 score.a = c(NA, 1, 1, 1, NA, NA, NA, NA, NA, NA, 1, NA))
  </code></pre>
  
  <p>Creates </p>
  
  <pre><code>   deid score.a
  1     5      NA
  2     5       1
  3     5       1
  4     5       1
  5     5      NA
  6    12      NA
  7    12      NA
  8    12      NA
  9    12      NA
  10   17      NA
  11   17       1
  12   17      NA
  </code></pre>
  
  <p>And I want to tell dplyr to keep cases that have any observations in <code>score.a</code>, including the NA values. Thus, I want it to return:</p>
  
  <pre><code>  deid score.a
  1     5      NA
  2     5       1
  3     5       1
  4     5       1
  5     5      NA
  6    17      NA
  7    17       1
  8    17      NA
  </code></pre>
  
  <p>I ran the code <code>help %&gt;% group_by(deid) %&gt;% filter(score.a &gt; 0)</code> however it pulls out the NAs as well. Thank you for any assistance. </p>
  
  <p>Edit: A similar question was asked here <a href="https://stackoverflow.com/questions/24583152/how-to-remove-groups-of-observation-with-dplyrfilter">How to remove groups of observation with dplyr::filter()</a>
  However, in the answer they use the 'all' condition and this requires use of the 'any' condition. </p>