/a></span>(<span class='st'>'2016-04-01'</span>), <span class='fu'><a href='https://www.rdocumentation.org/packages/base/topics/as.Date'>as.Date</a></span>(<span class='st'>'2017-04-01'</span>),
              <span class='kw'>by</span> <span class='kw'>=</span> <span class='st'>'month'</span>)[<span class='fu'><a href='https://www.rdocumentation.org/packages/base/topics/c'>c</a></span>(<span class='fl'>1</span>, <span class='fl'>4</span>, <span class='fl'>5</span>, <span class='fl'>7</span>, <span class='fl