/span>
<span><span class="co"># Including random slopes (only country as grouping variable)</span></span>
<span><span class="va">lmer_rs_1</span> <span class="op">&lt;-</span> <span class="kw">function</span><span class="op">(</span><span class="va">formula</span>, <span class="va">data</span>,<span class="va">...</span><span class="op">)</span> <span class="op">{</span></span>
<span>  <span class="kw"><a href="https://rdrr.io/r/base/library.html" class="external-link">require</a></span><span class="op">(</