tor</span>[N_test] y_test = y[permutation[N_train + <span class="dv">1</span> : N]];</span>
<span id="cb4-14"><a href="#cb4-14" aria-hidden="true" tabindex="-1"></a>}</span></code><button title="Copy to Clipboard" class="code-copy-button"><i class="bi"></i></button></pre></div>
<p>Recall that in Stan, <code>permutation[1:N_train]</code> is an array of integers, so that <code>x[permutation[1 : N_train]]</code> is a vector defined for <code>i in 1:N_train</code> by</p>
<div class="sourceCode" id="cb5"><pre cl