Re: Errors for bins with Negative Sumw

Thanks for reporting this special case when TH1::Sumw2 is called and the histogram has been filled.
The problem is now fixed in the SVN trunk.

Rene Brun

Hovhannes Khandanyan wrote:
>
> Dear ROOTers,
>
> In my analysis I have a histo h1 some of bins of which have negative
> fSumw (eg. bin=53):
> ...........
> fSumw[51]=6.865, x=1010
> fSumw[52]=0, x=1030
> fSumw[53]=-0.985, x=1050
> fSumw[54]=4.868, x=1070
> fSumw[55]=5.815, x=1090
> ................
> Further, I Clone() this histo to h2 which I need to h2->Scale() after
> having done h2->Sumw2(). Anyhow, when I do h2->IntegralAndError(...) I
> get 'nan' for the error. This I think is due to the fact the errors
> are not computed for bins with negative fSumw:
>
> ...............
> fSumw[51]=6.865, x=1010, error=2.62011
> fSumw[52]=0, x=1030, error=0
> fSumw[53]=-0.985, x=1050, error=nan
> fSumw[54]=4.868, x=1070, error=2.20635
> fSumw[55]=5.815, x=1090, error=2.41143
> .................
>
> So, please let me know if there is a work around this problem, so that
> I can get IntergalAndError() machinery running also for this
> particular case.
>
> Thank you,
> Hovhannes
>
Received on Wed Oct 27 2010 - 09:13:43 CEST