ss="fu"><a href="https://rdrr.io/r/base/colSums.html" class="external-link">rowSums</a></span><span class="op">(</span><span class="va">Z</span> <span class="op">*</span> <span class="va">b</span><span class="op">[</span><span class="va">id</span>, <span class="op">]</span><span class="op">)</span><span class="op">)</span></span></span>
<span class="r-in"><span><span class="va">DF</span><span class="op">$</span><span class="va">y</span> <span class="op">&lt;-</span> <span class="fu"><a href="https://rdrr.io