> <span class="op">&lt;-</span> <span class="fu"><a href="https://rdrr.io/pkg/EdSurvey/man/readPISA.html" class="external-link">readPISA</a></span><span class="op">(</span><span class="st">"~/PISA/2012"</span>, countries<span class="op">=</span><span class="st">"USA"</span><span class="op">)</span></span></span>
<span class="r-in"><span><span class="va">data</span> <span class="op">&lt;-</span> <span class="fu"><a href="https://rdrr.io/pkg/nlme/man/getData.html" class="external-link">getData</a></span><span