Hi Ray,
You should not confuse the role of
- TH1::Fill(x,1); //fill with a weight=1 (fEntries incremented by 1)
- TH1::Fill(x,w); //fill with a weight=w (fEntries incremented by 1)
- TH1::Fill(N,*x,*w);//fill with arrays x and weights w
//fEntries incremented by N
Rene Brun
redRay Fliller III wrote:
>
> Hello rooters,
>
> I am using ROOT 3.02/03 CVS as of Nov.12 on LINUX Mandrake.
>
> I have a class that inherits from a TH2F. If I try to subtract
> two of these historgrams, I get an empty histogram. To do the subtraction,
> I use TH1::Add(TH1 *h1, TH1 *h2, Double_t c1, Double_t c2), with
> c1=1,c2=-1. Obvious enough.
>
> But I notice that fEntries is zero for this. According to TH1.h,
> fEntries is the number of entries in the histogram. I assume that
> this is different than the number of bins. Looking at
> TH1::Fill(Axis_t x, Stat_t w) and TH2::Fill(Axis_t x, Axis_t y, Stat_t w)
> I see the fEntries is incremented only once. I get a different fEntries
> if I call TH1::Fill(x,1) N times vs. TH1::Fill(X,N).
>
> Is this a bug or a feature??
>
> --
>
> RAINMAN
> "How much does a piece of gum cost Ray?"
> "About $100."
> "How much does a new car cost Ray?"
> "`Bout $100."
> "There goes working for NASA!"
>
> ==================================================================
> Ray Fliller: rfliller@bnl.gov Office Phone: (631)-344-6124
> C-A Accelerator Physics Dept. Fax: (631)-344-5954
> Building 911B
> Brookhaven National Lab
> Upton, NY 11973 Office: Room 211
>
> http://www.agsrhichome.bnl.gov/People/rfliller/
> ==================================================================
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