**Public Function GammaIC( _
ByVal vA As Variant _
, ByVal vX As Variant _
) As Variant**

**Calculate the complementary incomplete Gamma function. **

**Examples:** GammaIC(1.0, 1.0) = 0.367879441171442
GammaIC(1.0, 2.0) = 0.135335283236613
GammaIC(2.0, 1.0) = 0.735758882342885
GammaIC(2.0, 2.0) = 0.406005849709838
GammaIC(2.2, 1.1) = 0.82996041174649
GammaIC(2.2, 1.1) = 1 - GammaI(2.2, 1.1)

**See also:** Gamma Function
GammaI Function
GammaIT Function
GammaILn Function
DGAMIC Function

**vA:** Function returns Null if vA is Null or cannot be fixed up to a Double precision floating point number.

**vX:** Function returns Null if vX is Null or cannot be fixed up to a Double precision floating point number. Evaluate the complementary incomplete Gamma function

GammaIC = integral from X to infinity of EXP(-T) * T^(A-1.)

GammaIC is evaluated for arbitrary real values of A and for non- negative values of X (even though DGAMIC is defined for X .LT. 0.0), except that for X = 0 and A .LE. 0.0, DGAMIC is undefined.

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. Copyright 1996-1999 Entisoft

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