Computation of the incomplete gamma function ratios and their inverse

@article{Didonato1986ComputationOT,
  title={Computation of the incomplete gamma function ratios and their inverse},
  author={A. Didonato and A. H. Morris},
  journal={ACM Trans. Math. Softw.},
  year={1986},
  volume={12},
  pages={377-393}
}
An algorithm is given for computing the incomplete gamma function ratios <italic>P</italic>(<italic>a</italic>, <italic>x</italic>) and <italic>Q></italic>(<italic>a</italic>, <italic>x</italic>) for <italic>a</italic> ⪈ 0, <italic>x</italic> ⪈ 0, <italic>a</italic> + <italic>x</italic> ≠ 0. Temme's uniform asymptotic expansions are used. The algorithm is robust; results accurate to 14 significant digits can be obtained. An' extensive set of coefficients for the Temme expansions is included. An… Expand
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A method is given for computing the incomplete gamma function ratio, P and its complement Q(a, x) for all real arguments a 0, x or = 0, which is efficient, yields both P and Q correctly to within 1 unit in the twelfth significant digit. Expand
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ACM Transactions on Mathematical Software
  • ACM Transactions on Mathematical Software
  • 1986
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