tan-dev/example-models/blob/master/misc/funnel/funnel.stan" class="uri">https://github.com/stan-dev/example-models/blob/master/misc/funnel/funnel.stan</a></p>
<p>Stan has trouble sampling from the region where <code>y</code>
is small and thus <code>x</code> is constrained to be near 0.
This is due to the fact that the density’s scale changes with <code>y</code>,
so that a step size that works well when <code>y</code> is large is inefficient
when <code>y</code> is small and vice-versa.</p>
<p>Running 4 cha