> <strong><code>digamma</code></strong><code>(T x)</code><br>
digamma function applied to x. The digamma function is the derivative
of the natural logarithm of the Gamma function. The function is
defined for positive numbers and non-integral negative numbers</p>
<!-- R; trigamma; (T x); -->
<p></p>
<p><code>R</code> <strong><code>trigamma</code></strong><code>(T x)</code><br>
trigamma function applied to x. The trigamma function is the second
derivative of the natural logarithm of the Gamma function</p>
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