jburkardt

ASA103\ The Digamma or Psi Function {#asa103-the-digamma-or-psi-function align=”center”} ===========================

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ASA103 is a C++ library which evaluates the digamma or psi function, by Jose Bernardo.

ASA103 is Applied Statistics Algorithm 103. Source code for many Applied Statistics Algorithms is available through STATLIB.

Licensing: {#licensing align=”center”}

The computer code and data files described and made available on this web page are distributed under the GNU LGPL license.

Languages: {#languages align=”center”}

ASA103 is available in a C version and a C++ version and a FORTRAN77 version and a FORTRAN90 version and a MATLAB version and a Python version.

Related Data and Programs: {#related-data-and-programs align=”center”}

ASA121, a C++ library which evaluates the trigamma function.

FN, a C++ library which approximates elementary and special functions using Chebyshev polynomials; functions include Airy, Bessel I, Bessel J, Bessel K, Bessel Y, beta, confluent hypergeometric, cosine integral, Dawson’s integral, digamma (psi), error, exponential integral, gamma, hyperbolic cosine integral, hyperbolic sine integral, incomplete gamma, log gamma, logarithmic integral, Pochhammer, psi, sine integral, Spence; by Wayne Fullerton.

TEST_VALUES, a C++ library which contains sample values for a number of distributions.

TOMS708, a FORTRAN90 library which includes routines to evaluate the digamma function.

Author: {#author align=”center”}

Original FORTRAN77 version by Jose Bernardo; C++ version by John Burkardt.

Reference: {#reference align=”center”}

1. Jose Bernardo,\ Algorithm AS 103: Psi ( Digamma ) Function,\ Applied Statistics,\ Volume 25, Number 3, 1976, pages 315-317.

Source Code: {#source-code align=”center”}

• asa103.cpp, the source code.
• asa103.hpp, the include file.

Examples and Tests: {#examples-and-tests align=”center”}

• asa103_prb.cpp, a sample calling program.
• asa103_prb_output.txt, the output file.

List of Routines: {#list-of-routines align=”center”}

• DIGAMA calculates DIGAMMA ( X ) = d ( LOG ( GAMMA ( X ) ) ) / dX
• PSI_VALUES returns some values of the Psi or Digamma function for testing.
• TIMESTAMP prints out the current YMDHMS date as a timestamp.

You can go up one level to the C++ source codes.

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Last revised on 18 January 2008.