Hi Julien, Sorry for the long delay to answer your mail Julien Bolmont wrote: >Hi, >>Sorry if this question has already been asked or seems stupid but I >really don't know what happen... >I really don't know how ROOT does to integrate TF1 and TH1... >For example, I send you a macro. If you run it, you will see (I hope >because it's what I see) that the integral of a product of a constant c >with a function f is not equal to the product of the constant c with >the integral of f. >The other problem is that the integral of the corresponding histogram >(TH1) is wrong too... I do not see any difference between the two methods. I Get the following output 8.34299e-06 OK 8.34299e-06 NOK !! (but it is OK) histo integral with "width" = 7.79905e-06 There is a difference between TF1::Integral and TH1::Integral. TF1::Integral is more precise. TH1::Integral can only assume a uniform distribution inside one bin. Rene Brun >I think I probably miss something important ! But what ? >Could you explain to me why these two cases leads to wrong results ? >Why the result with a TF1 is so different from the result obtained with >a TH1, even with a big number of bins ? >Thanks a lot for your answer ! >Julien.
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