From: Anna Kreshuk <anna.krechtchouk_at_cern.ch>

Date: Mon, 11 Apr 2005 14:18:48 +0200

Date: Mon, 11 Apr 2005 14:18:48 +0200

Hi,

As the comments to the TMath::Poisson function say, it is not equal to Poisson distribution for non-integer values of x. So, use TMath::PoissonI function instead, or, when computing the integral, start with an integer and take integer steps, and you will get what you expect. Example:

void test2()

{

Double_t sum = 0;

Int_t n = 10;

Double_t x;

for (Int_t i=0; i<n; i++) {

x = i;

sum+=TMath::Poisson(x, 1);

}

printf("sum = %f\n", sum);

}
Received on Mon Apr 11 2005 - 14:18:53 MEST

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