**Next message:**Rene Brun: "Re: [ROOT] Drawing a line in histogram in log mode"**Previous message:**Reinhardt Chamonal: "[ROOT] Drawing a line in histogram in log mode"**In reply to:**Rene Brun: "Re: [ROOT] error calc. in TProfile"**Next in thread:**Rene Brun: "Re: [ROOT] error calc. in TProfile"**Reply:**Rene Brun: "Re: [ROOT] error calc. in TProfile"**Messages sorted by:**[ date ] [ thread ] [ subject ] [ author ]

Hi Rene, RB>The computation of errors in TProfile has evolved with time RB>in case of bins with low statistics (1, 2 or 3 entries). RB>In version 3.02/07, we introduced a new condition, in case RB>the errors computed are very small (error/content <1e-6) RB>We had complaints from several users making fits on such profiles RB>and finding that too much weight was given to the points RB>with low statistics. RB>Any idea to improve the existing algorithm is welcome. as an old PAW user, I know that the error calculation within PAW has always been the source of major trouble. Now, errors calculated for histograms have a meaning (usually). Making fits, I need to be sure that the errors calculated for histograms are representative of the data. If in a certain bin in profile histograms there are only few entries, the error is going to be large (usually), independent of spread option or error-on-the-mean option. Now, when the error is large, the point will get a low weight in a fit, that's just how fits are set up to function. Therefore I can hardly understand how it can happen that such data points get large weights. Introducing a fix or a fudge every time someone complains does not seem to be a good policy; in the end we (as users) want to make serious physics with ROOT and need to be able to rely on such basic things like error calculation. I do not see, why the spread option and the error-on-the-mean options shold not suffice. They are meaningful and very (really!!!!) useful. just my .02$ Martin

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