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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