op">+</span> <span class="op">(</span><span class="va">Days</span><span class="op">|</span><span class="va">Subject</span><span class="op">)</span>, <span class="va">sleepstudy</span>, subset<span class="op">=</span><span class="va">Days</span><span class="op">&gt;=</span><span class="fl">2</span><span class="op">)</span><span class="op">)</span></span></span>
<span class="r-out co"><span class="r-pr">#&gt;</span> Linear mixed model fit by REML ['lmerMod']</span>
<span class="r-out co"><span class="r-pr">#&