 class="r-out co"><span class="r-pr">#&gt;</span>                  Within R2:  0.538111</span>
<span class="r-in"><span><span class="fu"><a href="https://rdrr.io/r/base/attr.html" class="external-link">attr</a></span><span class="op">(</span><span class="fu"><a href="https://rdrr.io/r/stats/vcov.html" class="external-link">vcov</a></span><span class="op">(</span><span class="va">est</span>, ssc <span class="op">=</span> <span class="fu">ssc</span><span class="op">(</span>K.fixef <span class="op">=</span> <s