title: Error in if-statement
body: <p>In R I have a data.frame <code>data</code> containing <code>user</code>, <code>game</code> and <code>number</code> which is the number of times a <code>game</code> has been played for a fixed <code>user</code>. </p>
  
  <p>Let a fixed user be given and consider this</p>
  
  <pre><code>user  game  number
  1     1     110
  1     2     95
  1     3     263
  1     4     55
  1     5     24
  1     6     10
  </code></pre>
  
  <p>Now Im looking for games that are dominant. A dominant game is a game than a user has played 25% of the times. 
  I want to find which games has been played more than 25% of the times in this case, so I type</p>
  
  <pre><code>u=c()
  for(j in 1:6) {
  # Check if the percentages is higher than 25
  if(data[j,3] / sum(data[,3]) &gt; 0.25) {
  u[j]=data[j,2]
  }
  else{u[j]=0}
  </code></pre>
  
  <p>But when I type this in R I get this strange message</p>
  
  <pre><code>Error in if(....): missing value where TRUE/FALSE needed
  </code></pre>