">(</span><span class="va">cdffiles</span><span class="op">)</span></span></span>
<span class="r-in"><span><span class="va">xset</span> <span class="op">&lt;-</span> <span class="fu">group</span><span class="op">(</span><span class="va">xset</span><span class="op">)</span></span></span>
<span class="r-in"><span><span class="va">xset2</span> <span class="op">&lt;-</span> <span class="fu"><a href="https://rdrr.io/pkg/xcms/man/retcor-methods.html" class="external-link">retcor</a></span><span class="op">(</span