ASA121
The Trigamma Function

ASA121 is a C++ library which evaluates the trigamma function, by BE Schneider.

ASA121 is Applied Statistics Algorithm 121. Source code for many Applied Statistics Algorithms is available through STATLIB.

Licensing:

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

Languages:

ASA121 is available in a C version and a C++ version and a FORTRAN77 version and a FORTRAN90 version and a MATLAB version.

Related Data and Programs:

ASA103, a C++ library which evaluates the digamma function.

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

Author:

Original FORTRAN77 version by BE Schneider; C++ version by John Burkardt.

Reference:

1. BE Schneider,
   Algorithm AS 121: Trigamma Function,
   Applied Statistics,
   Volume 27, Number 1, 1978, pages 97-99.

Source Code:

• asa121.cpp, the source code.
• asa121.hpp, the include file.
• asa121.sh, commands to compile the source code.

Examples and Tests:

• asa121_prb.cpp, a sample calling program.
• asa121_prb.sh, commands to compile and run the sample program.
• asa121_prb_output.txt, the output file.

List of Routines:

• TIMESTAMP prints out the current YMDHMS date as a timestamp.
• TRIGAM calculates trigamma(x) = d**2 log(gamma(x)) / dx**2
• TRIGAMMA_VALUES returns some values of the TriGamma function.

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