The Trigamma Function

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

ASA121 is Applied Statistics Algorithm 121.


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.


Original FORTRAN77 version by BE Schneider; FORTRAN90 version by John Burkardt.


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

Source Code:

Examples and Tests:

List of Routines:

You can go up one level to the FORTRAN90 source codes.

Last revised on 19 January 2008.