/span><span class="fl">3</span><span class="op">]</span>, each<span class="op">=</span><span class="fl">3</span><span class="op">)</span></span></span>
<span class="r-in"><span><span class="fu">rowGroupMeans</span><span class="op">(</span><span class="va">x</span>, groups<span class="op">=</span><span class="va">use_groups</span><span class="op">)</span></span></span>
<span class="r-out co"><span class="r-pr">#&gt;</span>                a            b           c</span>
<span class="r-out co"><span class="r