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When using the following values...

double a = 0;

double x = 0.2247;

double ans = MathNet.Numerics.SpecialFunctions.GammaUpperIncomplete(a, x);

...I am getting an answer of infinity.

This site: http://keisan.casio.com/exec/system/1180573447

...gives me the correct answer of 1.128

When I numerically integrate I also get an answer of approx. 1.128

What am I doing wrong when using your incomplete gamma function? The problem centers around using a value for a of zero.

Thanks! Love your math library!

double a = 0;

double x = 0.2247;

double ans = MathNet.Numerics.SpecialFunctions.GammaUpperIncomplete(a, x);

...I am getting an answer of infinity.

This site: http://keisan.casio.com/exec/system/1180573447

...gives me the correct answer of 1.128

When I numerically integrate I also get an answer of approx. 1.128

What am I doing wrong when using your incomplete gamma function? The problem centers around using a value for a of zero.

Thanks! Love your math library!

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## comments

cdrnet wrote Jun 30, 2014 at 4:00 PM

For a = 0 this functions becomes the exponential integral (Ei) function. It would be great if we could add this function (and extend GammaUpperIncomplete to a=0) to support this case.

Could you open an issue on this over at Github https://github.com/mathnet/mathnet-numerics? We don't use Codeplex for issues.

Thanks,

Christoph