TOMS435
Modified Incomplete Gamma Function

TOMS435 is a FORTRAN77 library which implements ACM TOMS algorithm 435, which evaluates the modified incomplete Gamma function.

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.

Related Data and Programs:

ASA032, a FORTRAN77 library which evaluates the incomplete Gamma function.

ASA147, a FORTRAN77 library which evaluates the incomplete Gamma function.

ASA239, a FORTRAN77 library which evaluates the incomplete Gamma function.

TEST_VALUES, a FORTRAN77 library which contains routines which return sample values of various functions, including the modified beta function, and the logarithm of the gamma function.

Usage:

value = gaminc ( a, x1, x2, gam )

computes the exponential of X1 times the integral from X1 to X2 of |y|^(A-1) * exp(-y) dy, returning the value as GAMINC. The user must supply in GAM the value of the Gamma function of A.

Reference:

1. Wayne Fullerton,
   Algorithm 435: Modified Incomplete Gamma Function,
   Communications of the ACM,
   Volume 15, Number 11, November 1972, pages 993-995.

Source Code:

• toms435.f, the source code.
• toms435.sh, commands to compile the source code.

Examples and Tests:

• toms435_prb.f, a sample calling program.
• toms435_prb.sh, commands to compile and run the sample program.
• toms435_prb_output.txt, the output file.

List of Routines:

• GAMINC evaluates the modified incomplete Gamma function.
• GAMMA_INC_VALUES returns some values of the incomplete Gamma function.
• GAMMA evaluates the Gamma function.
• TIMESTAMP prints out the current YMDHMS date as a timestamp.

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