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GammaRelatedGamma(Double, Double) Method

Evaluate the complementary incomplete Gamma function Gamma(a,z0) = integral from z0 to infinity of exp(-t) * t**(a-1) The order of parameters is the same as the Mathematica function Gamma[a,z0]. Gamma(a,z0) is evaluated for arbitrary real values of A and for non-negative values of x (even though Gamma is defined for z0 < 0.0), except that for z0 = 0 and a <= 0.0, Gamma is undefined.

Namespace: Altaxo.Calc
Assembly: AltaxoCore (in AltaxoCore.dll) Version: 4.8.3179.0 (4.8.3179.0)
Syntax
C#
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public static double Gamma(
	double a,
	double z0
)

Parameters

a  Double
The function argument.
z0  Double
The lower boundary of integration.

Return Value

Double
Complementary incomplete Gamma function of arguments a and z0.
Remarks
C#
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A slight deterioration of 2 or 3 digits accuracy will occur when
GammaIC is very large or very small in absolute value, because log-
arithmic variables are used.  Also, if the parameter A is very close
to a negative integer (but not a negative integer), there is a loss
of accuracy, which is reported if the result is less than half
machine precision.

This is a translation from the Fortran version of DGAMIC, SLATEC, FNLIB,
CATEGORY C7E, REVISION 920528, originally written by Fullerton W.,(LANL)
to C++.

References:

(1) W. Gautschi, A computational procedure for incomplete
    gamma functions, ACM Transactions on Mathematical
    Software 5, 4 (December 1979), pp. 466-481.
(2) W. Gautschi, Incomplete gamma functions, Algorithm 542,
    ACM Transactions on Mathematical Software 5, 4
    (December 1979), pp. 482-489.

Routines called: d9gmit, d9gmic, d9lgic, d9lgit, LnGamma(x), LnGamma(x,a)
See Also