asa103, a FORTRAN77 code which evaluates the digamma or psi function, by Jose Bernardo.
This is a version of Applied Statistics Algorithm 103.
The computer code and data files described and made available on this web page are distributed under the MIT license
asa103 is available in a C version and a C++ version and a Fortran90 version and a MATLAB version and an Octave version and a Python version.
ASA121, a FORTRAN77 code which evaluates the trigamma function.
FN, a FORTRAN77 library which approximates elementary and special functions using Chebyshev polynomials; functions include Airy, Bessel I, Bessel J, Bessel K, Bessel Y, beta, confluent hypergeometric, cosine integral, Dawson's integral, digamma (psi), error, exponential integral, gamma, hyperbolic cosine integral, hyperbolic sine integral, incomplete gamma, log gamma, logarithmic integral, Pochhammer, psi, sine integral, Spence; by Wayne Fullerton.
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.
Original FORTRAN77 version by Jose Bernardo; This version by John Burkardt.