rse transform</h3>
<p>The inverse transform for an unconstrained <span class="math inline">\(y \in \mathbb{R}^K\)</span> to an
ordered sequence <span class="math inline">\(x \in \mathbb{R}^K\)</span> is defined by the recursion</p>
<p><span class="math display">\[
x_k
=
\left\{
\begin{array}{ll}
y_1 &amp; \mbox{if } k = 1, \mbox{ and}
\\
x_{k-1} + \exp(y_k) &amp; \mbox{if } 1 &lt; k \leq K.
\end{array}
\right.
\]</span></p>
<p><span class="math inline">\(x_k\)</span> can also be expressed iteratively as</p>