title: The percent sign in R
body: <p>I recently read some source code for a R package called 'pathifier'. In the source code, it uses the percent sign. </p>
  
  <pre><code>if (0 %in% xs) {
  si &lt;- NULL
  cat(file = logfile, append = TRUE, "skipping pathway ", 
  i, " (0 in xs)\n")
  }
  </code></pre>
  
  <p>What does <code>%in%</code> mean in this function? Does it just mean the regular 'in'?</p>