Computation of the Incomplete Gamma Function Ratios
NAVAL SURFACE WEAPONS CENTER DAHLGREN LAB VA
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A method, made up of several algorithms, is given for computing the incomplete gamma function ratio, Pa, x and its complement Qa, x for all real arguments a 0, x or 0. The difficult case when a and x are large is treated by a modified version of Takenagas method. The resulting computer program is efficient, yields both P and Q correctly to within 1 unit in the twelfth significant digit, or, at the users option, to within one unit in the sixth or third significant digit. A FORTRAN listing of the program is included.
- Theoretical Mathematics
- Computer Programming and Software