n level2">
<h2 id="regression-function">2. Regression function<a class="anchor" aria-label="anchor" href="#regression-function"></a>
</h2>
<p>After exploring the data, we define the regression function. Here we
use a linear-plateau-linear function with five parameters: t1, t2, t3,
k, and <span class="math inline">\(\beta\)</span>. The function can be
expressed mathematically as follows:</p>
<p><code><a href="../reference/fn_lin_pl_lin.html">fn_lin_pl_lin()</a></code></p>
<p><span class="math display">\[\beg