s="p">,</span><span class="n">pchunk</span>

    <span class="n">pchunk</span><span class="o">=</span><span class="n">params</span><span class="p">%</span><span class="n">pchunk</span>

    <span class="n">dr</span><span class="o">=</span><span class="n">F</span><span class="p">%</span><span class="n">r_1D</span><span class="p">(</span><span class="mi">2</span><span class="p">)</span><span class="o">-</span><span class="n">F</span><span class="p">%</span><span class="n">r_1D</span><span class="p">(</span><s