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# Gamma Lower Reg

The regularized lower incomplete Gamma integral
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## GammaLower Reg

 doublegammaLower_reg( double a double x )
The regularized lower portion of the incomplete Gamma integral. This is also sometime referred to as the left tail of the integral, i.e



## Accuracy:

Tested at random a, x.
Relative error:
domain     # trials      peak         rms
0,30       200000       3.6e-14     2.9e-15
0,100      300000       9.9e-14     1.5e-14


## Example:

#include <stdio.h>
#include <codecogs/maths/special/gamma/gamma_lower_reg.h>
void main
{
for(double a=0; a<3; a+=0.25)
{
double y=Maths::Special::Gamma::gammaLower_reg(a, 2);
printf("\n gammaLower_reg(%lf, 2)=%lf", a,y);
}
}

## Output:

gammaLower_reg(0.000000, 2)=1.000000
gammaLower_reg(0.250000, 2)=0.982714
gammaLower_reg(0.500000, 2)=0.954500
gammaLower_reg(0.750000, 2)=0.914944
gammaLower_reg(1.000000, 2)=0.864665
gammaLower_reg(1.250000, 2)=0.805153
gammaLower_reg(1.500000, 2)=0.738536
gammaLower_reg(1.750000, 2)=0.667294
gammaLower_reg(2.000000, 2)=0.593994
gammaLower_reg(2.250000, 2)=0.521056
gammaLower_reg(2.500000, 2)=0.450584
gammaLower_reg(2.750000, 2)=0.384266

## References:

Cephes Math Library Release 2.8: June, 2000

### Note

In this implementation, both parameters must be positive.

### Parameters

 a input argument x upper positive limit of the integral.

### Authors

Stephen L.Moshier. Copyright 1984, 1987, 1989, 1992, 2000
Documented and Updated by Will Bateman
##### Source Code

Source code is available when you agree to a GP Licence or buy a Commercial Licence.

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