# Fungrim entry: f1527d

Symbol: DigammaFunction $\psi\!\left(z\right)$ Digamma function
DigammaFunction(z), rendered as $\psi\!\left(z\right)$, represents the digamma function of argument $z$.
DigammaFunction(z, m), rendered as $\psi^{(m)}\!\left(z\right)$, represents the order $m$ derivative of the digamma function of argument $z$. This is also known as the polygamma function of order $m$ and argument $z$. The case $m = 1$ (rendered as $\psi'\!\left(z\right)$ ) is sometimes called the trigamma function, $m = 2$ the tetragamma function, etc.
Definitions:
Fungrim symbol Notation Short description
DigammaFunction$\psi\!\left(z\right)$ Digamma function
Source code for this entry:
Entry(ID("f1527d"),
SymbolDefinition(DigammaFunction, DigammaFunction(z), "Digamma function"),
Description(SourceForm(DigammaFunction(z)), ", rendered as", DigammaFunction(z), ", represents the digamma function of argument", z, "."),
Description(SourceForm(DigammaFunction(z, m)), ", rendered as", DigammaFunction(z, m), ", represents the order", m, "derivative of the digamma function of argument", z, ". ", "This is also known as the polygamma function of order", m, "and argument", z, ". ", "The case", Equal(m, 1), "(rendered as ", DigammaFunction(z, 1), ") is sometimes called the trigamma function, ", Equal(m, 2), "the tetragamma function, etc."))

## Topics using this entry

Copyright (C) Fredrik Johansson and contributors. Fungrim is provided under the MIT license. The source code is on GitHub.

2021-03-15 19:12:00.328586 UTC