Hi Michael,
I cannot reproduce this problem.
Which version are you using? which machine?
Did you compile yourself from the source?
Rene Brun
On Sun, 19 Oct 2003, Michael
Gold wrote:
>
> the function
> Double_t TMath::Poisson(Double_t x, Double_t par)
> {
> // compute the Poisson distribution function for (x,par)
>
> if (x<0) return 0;
> if (x==0) return TMath::Exp(-par);
> return TMath::Power(par,x)/TMath::Gamma(x+1)/TMath::Exp(par);
> }
>
>
> dosn't appear to work for x=0.... cannot imagine what the problem is!
>
>
> root [28] TMath::Poisson(0.,2.)
> (Double_t)0.00000000000000000e+00
> root [29] TMath::Poisson(1.,2.)
> (Double_t)2.70670566473225516e-01
> root [30] TMath::Poisson(2.,2.)
> (Double_t)2.70670566473225516e-01
> root [31]
>
>
>
> root [31]
> root [31] TMath::Power(2,0)/TMath::Gamma(0+1)/TMath::Exp(2)
> (double)1.35335283236612702e-01
> root [32] TMath::Power(2,1)/TMath::Gamma(1+1)/TMath::Exp(2)
> (double)2.70670566473225516e-01
> root [33] TMath::Power(2,2)/TMath::Gamma(2+1)/TMath::Exp(2)
> (double)2.70670566473225516e-01
>
>
>
>
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