 arguments must be expressions involving only data, transformed data, and generated quantity variables.</p>
<p>In user-defined functions, the qualifier <code>data</code> may be placed before an argument type declaration to indicate that the argument must be data only. For example,</p>
<div class="sourceCode" id="cb9"><pre class="sourceCode stan code-with-copy"><code class="sourceCode stan"><span id="cb9-1"><a href="#cb9-1" aria-hidden="true" tabindex="-1"></a><span class="dt">real</span> foo(<span class="kw