n> <span class="op">~</span> <span class="fu"><a href="https://rdrr.io/r/stats/poly.html" class="external-link">poly</a></span><span class="op">(</span><span class="va">year</span>, <span class="fl">2</span><span class="op">)</span> <span class="op">|</span> <span class="va">id</span>, control <span class="op">=</span> <span class="fu"><a href="https://rdrr.io/pkg/nlme/man/lmeControl.html" class="external-link">lmeControl</a></span><span class="op">(</span>opt <span class="op">=</span> <span class="st">'opt