set</a></span><span class="op">(</span><span class="va">Y</span>, select <span class="op">=</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">"A1"</span>, <span class="st">"A2"</span>, </span></span>
<span class="r-in"><span>                          <span class="st">"gender"</span>, <span class="st">"education"</span><span class="op">)</span><span class="op">)</span></span></span>
<span class="r-in"><span></span></spa