TOMS179 is a Python library which implements ACM TOMS algorithm 179, for evaluating the modified Beta function.
While the text of many ACM TOMS algorithms is available online through ACM: http://www.acm.org/pubs/calgo or NETLIB: http://www.netlib.org/toms/index.html, many of the early algorithms are not available. This is one of them. I typed it in.
The original algorithm was published in the Algol language. Shortly therafter, a distinct FORTRAN77 algorithm was published as a "remark" to the original algorithm. A few modifications to the FORTRAN77 program were proposed in a subsequent "remark".
prob = mdbeta ( x, p, q )where
TOMS179 is available in a C version and a C++ version and a FORTRAN77 version and a FORTRAN90 version and a MATLAB version and a Python version.
TEST_VALUES, a Python library which contains routines which return sample values of various functions, including the modified beta function, and the logarithm of the gamma function.
You can go up one level to the Python source codes.