ASA103
The Digamma or Psi Function

ASA103 is a FORTRAN77 library which evaluates the digamma or psi function.

ASA103 is Applied Statistics Algorithm 103. Source code for many Applied Statistics Algorithms is available through STATLIB.

Languages:

ASA103 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:

ASA121, a FORTRAN77 library which evaluates the trigamma function.

SPECFUN, a FORTRAN77 library which computes special functions, including the Psi or Digamma function.

TEST_VALUES, a FORTRAN77 library which contains sample values for a number of distributions.

TOMS708, a FORTRAN77 library which includes routines to evaluate the digamma function.

Reference:

1. Jose Bernardo,
   Algorithm AS 103: Psi ( Digamma ) Function,
   Applied Statistics,
   Volume 25, Number 3, 1976, pages 315-317.

Source Code:

• asa103.f, the source code.
• asa103.sh, commands to compile the source code.

Examples and Tests:

• asa103_prb.f, a sample calling program.
• asa103_prb.sh, commands to compile and run the sample program.
• asa103_prb_output.txt, the output file.

List of Routines:

• DIGAMA calculates DIGAMMA ( X ) = d ( LOG ( GAMMA ( X ) ) ) / dX
• PSI_VALUES returns some values of the Psi or Digamma function for testing.
• TIMESTAMP prints out the current YMDHMS date as a timestamp.

You can go up one level to the FORTRAN77 source codes.