Hi Burt,
Yep. This has been a topic of discussion in PHENIX computing recently.
Here are the lines that do the deed (H_H1.cxx:1546-1550):
if (fu < 1.e-9) fu = 1.e-9;
icu = Int_t(cu);
fsub = -fu + cu * TMath::Log(fu);
fobs = hFitter->GetSumLog(icu);
The bin contents are floor()'ed. I suppose one could argue that since
the log likelihood procedure in TH1::Fit happens to assume a poisson
probability for sampling the observed bin contents from the model you're
on somewhat sketchy ground if the bins don't contain integer values, but
I think the last line above should be changed to
fobs = hFitter->GetSumLog(cu);
if only to avoid needless surprises.
Cheers,
Dave
Burt Holzman wrote:
> It seems that log-likelihood fitting is integerizing bin
> contents before fitting. Is this intended behavior?
--
David Morrison Brookhaven National Laboratory phone: 631-344-5840
Physics Department, Bldg 510 C fax: 631-344-3253
Upton, NY 11973-5000 email: dave@bnl.gov
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