s columns of dates, flow values, and (optional) groups (e.g. station numbers).
Leave blank or set to <code>NULL</code> if using <code>station_number</code> argument.</p></dd>


<dt>dates</dt>
<dd><p>Name of column in <code>data</code> that contains dates formatted YYYY-MM-DD. Only required if dates column name is not 
'Date' (default). Leave blank or set to <code>NULL</code> if using <code>station_number</code> argument.</p></dd>


<dt>values</dt>
<dd><p>Name of column in <code>data</code> that contains num