le, the following is legal.</p>
<pre class="stan"><code>array[I, J, K] real x;
array[J, K] real y;
array[K] real z;
// ...
x[1] = y;
x[1, 1] = z;</code></pre>
<p>The sizes must match. Here, <code>x[1]</code> is a <code>J</code> by <code>K</code>
array, as is <code>y</code>.</p>
<p>Partial array assignment also works for arrays of matrices, vectors,
and row vectors.</p>
</div>
<div id="mixing-array-vector-and-matrix-types" class="section level3 unnumbered">
<h3>Mixing array, vector, and matrix types</h3>
<p>