an><span class="op">)</span>, <span class="fu"><a href="https://rdrr.io/r/base/Extremes.html" class="external-link">max</a></span><span class="op">(</span><span class="va">year</span><span class="op">)</span>, length.out <span class="op">=</span> <span class="fl">15</span><span class="op">)</span>,</span></span>
<span class="r-in"><span>    group <span class="op">=</span> <span class="fu"><a href="https://rdrr.io/r/base/levels.html" class="external-link">levels</a></span><span class="op">(</span><span class