Hi Ben, I do not see anything wrong with the cut mechanism. I tested a similar example with no problems. My guess is that you forgot to divide the histogram by the bin width !! You forgot to attach the files, so I cannot be more precise, but I am pretty convince that you forgot to take into account the bin width. Rene Brun On Wed, 3 Jan 2001, Benjamin E. Norman wrote: > 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 > ````:````:````:````:````:````:````:````:````:````:````:```` >
This archive was generated by hypermail 2b29 : Tue Jan 01 2002 - 17:50:33 MET