f the argument <code>functional_forms</code> is specified with the value <code>"logit_cubic"</code>, <span class="math inline">\(g()\)</span> is the complementary log-log link function and the linear predictor of <span class="math inline">\(P_R(t)\)</span> is a cubic polynomial in <span class="math inline">\(t\)</span>, so that:</p>
<p><span class="math display">\[\begin{equation}
    \ln{\left(\frac{P_R(t)}{1-P_R(t)}\right)} = \beta_0 + \beta_1t + \beta_2t^2 + \beta_3t^3
\end{equation}\]</span></p>
<p>In b