o"><span class="r-pr">#&gt;</span>    ⎢──────────────────────────  - ───────────────────────────── + ───────────────</span>
<span class="r-out co"><span class="r-pr">#&gt;</span>    ⎢                       2                               2                     </span>
<span class="r-out co"><span class="r-pr">#&gt;</span>    ⎣ (exp(b₁⋅(x - x₀)) + 1)          