uin_model</span> <span class="op">&lt;-</span> <span class="fu">lme4</span><span class="fu">::</span><span class="fu"><a href="https://rdrr.io/pkg/lme4/man/lmer.html" class="external-link">lmer</a></span><span class="op">(</span><span class="va">heartrate</span> <span class="op">~</span> <span class="va">depth</span> <span class="op">+</span> <span class="va">duration</span> <span class="op">+</span> <span class="op">(</span><span class="fl">1</span><span class="op">|</span><span class="va">bird</span><span