title: How to filter data frame by range of row values with R?
body: <p>I have a following data frame and i want to filter the data frame that only contains values from 2019-06-01 to 2019-06-30</p>
  <pre><code>    ds            yhat
  1   2015-01-01    -100
  2   2015-01-02     250
  3   2015-01-03      50
  4   …               60
  5   2019-06-30     370
  </code></pre>