de r"><code><span><span class="fu">plot_density_2D</span><span class="op">(</span></span>
<span>  <span class="va">sessions</span>,</span>
<span>  bins <span class="op">=</span> <span class="fl">15</span>,</span>
<span>  by <span class="op">=</span> <span class="fu"><a href="https://rdrr.io/r/base/c.html" class="external-link">c</a></span><span class="op">(</span><span class="st">"wday"</span>, <span class="st">"month"</span>, <span class="st">"year"</span><span class="op">)</span>,</span>
<span>  start <sp