"https://rdrr.io/r/base/data.frame.html" class="external-link">data.frame</a></span><span class="op">(</span><span class="va">Z</span>, <span class="va">X</span>, <span class="va">U</span>, <span class="va">D</span><span class="op">)</span></span></span>
<span class="r-in"><span><span class="va">x</span> <span class="op">&lt;-</span> <span class="fu">standardize_level</span><span class="op">(</span></span></span>
<span class="r-in"><span>  fitter_list <span class="op">=</span> <span class="fu"><a href="http