at2</span><span class="op">)</span></span>
<span></span>
<span><span class="co"># Have a look at the new columns</span></span>
<span><span class="va">dat3</span><span class="op">[</span><span class="fl">1</span><span class="op">:</span><span class="fl">5</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="st">"year"</span>, <span class="st">"month"</span>, <span class="st">"day"</span><span class="op">)</span><span class="o