ASA121
The Trigamma Function

ASA121 is a FORTRAN90 library which evaluates the trigamma function, by BE Schneider.

ASA121 is Applied Statistics Algorithm 121.

Languages:

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

Related Data and Programs:

ASA103, a FORTRAN90 library which evaluates the digamma function.

TEST_VALUES, a FORTRAN90 library which contains sample values for a number of special functions.

Author:

Original FORTRAN77 version by BE Schneider; FORTRAN90 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.f90, the source code.

Examples and Tests:

• asa121_test.f90, a sample calling program.
• asa121_test.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 FORTRAN90 source codes.