title: Split a data frame by median
body: <p>I would like to divide my data based on the median into high and low. I want to put it in one column.</p>
  <pre class="lang-r prettyprint-override"><code>df &lt;- data.frame(salary = c(623.3,515.2,611.0,729.0,843.25), stringsAsFactors = FALSE)
  </code></pre>