Computation of the Incomplete Gamma Function Ratios

Abstract

A method, made up of several algorithms, is given for computing the incomplete gamma function ratio, P(a, x) and its complement Q(a, 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 Takenaga's 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 user's option, to within one unit in the sixth or third significant digit. A FORTRAN listing of the program is included.

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Document Details

Document Type
Technical Report
Publication Date
Apr 01, 1976
Accession Number
ADA031812

Entities

People

  • A. R. Didonato
  • R. K. Hageman

Organizations

  • Naval Surface Warfare Center Dahlgren Division

Tags

Communities of Interest

  • Air Platforms
  • Energy and Power Technologies

DTIC Thesaurus Topics

  • Accuracy
  • Algorithms
  • Asymptotic Series
  • Coefficients
  • Computations
  • Computer Programs
  • Computers
  • Data Science
  • Equations
  • Errors
  • Inequalities
  • Information Science
  • Integrals
  • Lepidoptera
  • Numbers
  • Plastic Explosives
  • Statistics

Readers

  • Approximation Theory.
  • Computer Science.