 the slowest and the last index changes the fastest.</p>
<p>To see how this works, consider a 3-dimensional variable with dimension sizes 2, 3, and 4,
e.g., an array of matrices, a 2-D array of vectors or row_vectors, or a 3-D array of scalars.
Given a Stan program with model parameter variable:</p>
<pre><code> real foo[2, 3, 4];</code></pre>
<p>The Stan CSV file will require 24 columns to output the elements of <code>foo</code>.
The first 6 columns will be labeled:</p>
<pre><code>foo.1.1.1, foo.1.1.2, foo.