XLPack 6.1
Excel VBA Numerical Library Reference Manual
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◆ Gammap()

Function Gammap ( A As  Double,
X As  Double,
Optional Info As  Long 
)

Normalized incomplete gamma function P(a, x)

Purpose
This routine computes the normalized incomplete gamma function P(a, x).
P(a, x) = γ(a, x)/Γ(a) = (1/Γ(a))∫ t^(a-1)*exp(-t) dt [0, x]
Returns
Double
Normalized incomplete gamma function P(a, x).
Parameters
[in]AArgument a. (A > 0)
[in]XArgument x. (X >= 0)
[out]Info= 0: Successful exit.
= -1: The argument A had an illegal value. (A <= 0)
= -2: The argument X had an illegal value. (X < 0)
= 1: Floating point range error.
Reference
boost/math/special_functions