ASA121
The Trigamma Function

ASA121 is a MATLAB 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 MATLAB library which evaluates the digamma function.

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

Author:

Original FORTRAN77 version by BE Schneider; MATLAB 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:

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

Examples and Tests:

• asa121_test.m, a sample calling program.
• asa121_test01.m, tests TRIGAM.
• asa121_test_output.txt, the output file.

You can go up one level to the MATLAB source codes.