s, because the logarithm function
isn’t linear and hence doesn’t distribute through averages (Jensen’s
inequality shows which way the inequality goes). The right thing to
do is to apply <code>log_sum_exp</code> of the posterior draws of
<code>log_p_y_tilde</code>. The average log predictive density is then
given by subtracting <code>log(N_new)</code>.</p>
</div>
<div id="clustering-and-similarity" class="section level4">
<h4 class="unnumbered" number="">Clustering and similarity</h4>
<p>Often a mixtur