    <span class="st">"2014-03-13"</span>, <span class="st">"2014-02-23"</span>, <span class="st">"2014-04-03"</span>,</span>
<span class="r-in">                          <span class="st">"2014-01-08"</span>, <span class="st">"2014-01-08"</span><span class="op">)</span></span>
<span class="r-in"><span class="va">date_of_registration</span> <span class="op">&lt;-</span> <span class="fu"><a href="https://rdrr.io/r/base/c.html" class="external-link">c</a></span><span class="op">(</span><span class="cn">NA</sp