Hi Rooters, I have a problem with some code, and I was wondering if anyone has any suggestions. I'm trying to calculate dN/dpt^2 (1/pt dN/dpt) for some simulated data, and I get what seems to me like a strange inconsistency. The first time I tried it, I did the following: TCut isFinalState = "1<=ks && ks<=10"; TCut isHminus = "kf==-211 || kf==-321 || kf==-2212"; TCut isMidRapidity = "abs(eta) < 0.5"; tree->Draw("pt>>histoDnDpt2", "1./pt" * (isFinalState && isHminus && isMidRapidity)); This gives me the red curve on the enclosed graph. This didn't seem right, so I tried the following: tree->Draw("pt>>histoDnDpt2b", (isFinalState && isHminus && isMidRapidity)); TF1* fIdentity = new TF1("fIdentity", "x"); histoDnDpt2b->Divide(fIdentity); This gives me blue curve. I can understand that there will be some slight differences due to using the pt at the bin center in the second case, but this does not explain my problem. The difference in the curves at pt=0.2 GeV is a factor of 10, while the maximum difference in pt between the bin center and the bin edge is (0.2/0.005)=2.5%. So....am I missing something fundamental about histograms? Thanks, Ben ,,,,:,,,,:,,,,:,,,,:,,,,:,,,,:,,,,:,,,,:,,,,:,,,,:,,,,:,,,, Benjamin Norman http://kent.edu/~bnorman Department of Physics bnorman@kent.edu Kent State University, OH, USA 330-672-0378 ````:````:````:````:````:````:````:````:````:````:````:````
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