"cn">NULL</span>,</span>
<span>    Product <span class="op">=</span> <span class="cn">NULL</span>, </span>
<span>    <span class="co"># Ensure that all energy values are positive, as required for analysis.</span></span>
<span>    E.ktoe <span class="op">=</span> <span class="fu"><a href="https://rdrr.io/r/base/MathFun.html" class="external-link">abs</a></span><span class="op">(</span><span class="va">E.ktoe</span><span class="op">)</span></span>
<span>  <span class="op">)</span></span>
<span><span class="fu