TOMS435
Modified Incomplete Gamma Function

TOMS435 is a FORTRAN77 program, using single precision arithmetic, 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 is a FORTRAN77 library which evaluates the incomplete Gamma function.

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

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

TEST_VALUES 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.csh, commands to compile the source code.

Examples and Tests:

• toms435_prb.f, a sample calling program.
• toms435_prb.csh, 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.