"fu"><a href="https://rdrr.io/r/base/c.html" class="external-link">c</a></span><span class="op">(</span><span class="va">x2</span>, <span class="op">-</span><span class="fl">91</span><span class="op">)</span></span>
<span><span class="va">x2</span></span>
<span><span class="co">#&gt; &lt;declared&lt;numeric&gt;[7]&gt;</span></span>
<span><span class="co">#&gt; [1]       1       2       3       4       5 NA(-91) NA(-91)</span></span>
<span><span class="co">#&gt; Missing values: -91</span></span>
<span><span 