a.frame</a></span><span class="op">(</span>AUC <span class="op">=</span> <span class="fl">0.6</span>, D <span class="op">=</span> <span class="fl">0.3</span><span class="op">)</span><span class="op">)</span></span></span>
<span class="r-in"><span>  <span class="va">optree</span> <span class="op">&lt;-</span> <span class="fu"><a href="natural_join.html">natural_join</a></span><span class="op">(</span><span class="va">d1</span>, <span class="va">d2</span>, by <span class="op">=</span> <span class="st">"AUC"</