title: Remove participants based on a certain criteria
body: <p>I have an experiment with numerous participants and their choices. 
  For simplicity, let's assume the following: </p>
  
  <pre><code>part&lt;-c(1,1,1,2,2,2,3,3,3)
  choice&lt;-c(6,2,9,2,3,18,3,6,8)
  study&lt;-cbind(part,choice)
  
         part choice
   [1,]    1      6
   [2,]    1      2
   [3,]    1      9
   [4,]    2      2
   [5,]    2      3
   [6,]    2     18
   [7,]    3      3
   [8,]    3      6
   [9,]    3      8
  </code></pre>
  
  <p>Now, I would like to <strong>entirely</strong> remove certain participants. For example those who made at least one choice above 10. So in the example above, because participant 2, made one choice above 10, I entirely remove him: The final data should look: </p>
  
  <pre><code>      part choice
  [1,]    1      6
  [2,]    1      2
  [3,]    1      9
  [4,]    3      3
  [5,]    3      6
  [6,]    3      8
  </code></pre>
  
  <p>How can I do it? </p>
  
  <p>Thanks! </p>