ASA121
The Trigamma Function

ASA121 is a MATLAB library, using double precision arithmetic, which evaluates the trigamma function.

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

Related Data and Programs:

ASA103 is a MATLAB library which evaluates the digamma function.

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

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

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.
• trigam.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.