is gammaupperincomplete correct?


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!
Closed Jun 30, 2014 at 3:00 PM by cdrnet
Please use Github instead. Thanks.


cdrnet wrote Jun 30, 2014 at 3:00 PM

GammaUpperIncomplete currently only supports a > 0 and x > 0 (according to docs).

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.