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.
The computer code and data files described and made available on this web page are distributed under the GNU LGPL license.
ASA121 is available in a C version and a C++ version and a FORTRAN77 version and a FORTRAN90 version and a MATLAB version.
ASA103, a MATLAB library which evaluates the digamma function.
TEST_VALUES, a MATLAB library which contains sample values for a number of special functions.
Original FORTRAN77 version by BE Schneider; MATLAB version by John Burkardt.
You can go up one level to the MATLAB source codes.