ndix" class="section level2">
<h2 number="25.4"><span class="header-section-number">25.4</span> Digamma</h2>
<p>The digamma function <span class="math inline">\(\Psi\)</span> is the derivative of the <span class="math inline">\(\log \Gamma\)</span>
function, <span class="math display">\[ \Psi(u) \ = \ \frac{d}{d u} \log \Gamma(u) \ = \
\frac{1}{\Gamma(u)} \ \frac{d}{d u} \Gamma(u). \]</span></p>

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