" class="external-link">ncol</a></span><span class="op">(</span><span class="va">fdata.Reg.tr</span><span class="op">)</span><span class="op">]</span>, collapse <span class="op">=</span> <span class="st">" + "</span><span class="op">)</span></span></span>
<span class="r-in"><span><span class="va">form</span> <span class="op">&lt;-</span> <span class="fu"><a href="https://rdrr.io/r/stats/formula.html" class="external-link">formula</a></span><span class="op">(</span><span class="fu"><a href="https://rdrr.io/r