have a vector of <code>K</code> parameters for each of <code>J</code> groups; this can be declared using</p>
<div class="sourceCode" id="cb12"><pre class="sourceCode stan code-with-copy"><code class="sourceCode stan"><span id="cb12-1"><a href="#cb12-1" aria-hidden="true" tabindex="-1"></a><span class="dt">array</span>[J] <span class="dt">vector</span>[K] theta;</span></code><button title="Copy to Clipboard" class="code-copy-button"><i class="bi"></i></button></pre></div>
<p>Then <code>theta[j]</code> is an 