Hi Rene, I am affraid that the problem is somewhat different. I understand that I can of course define histogram myhist with desired binning. But in case of time it is however not always obvious what is the proper range. Therefore I am using automatical binning option for fast checking of time dependencies... The following script example.C illustrates my problem: { UInt_t t0; UInt_t fSize; UInt_t fTime; TFile *f = new TFile("test.root","RECREATE"); TTree *T = new TTree("T","test"); t0=time(NULL); T->Branch("Size",&fSize,"Size/i"); T->Branch("Time",&fTime,"Time/i"); fTime=t0; for(int i=0;i<1000;i++){ fTime++; fSize=i/10; T->Fill(); } T->Write(); } root [0] .x example.C //the following cases gives nice detailed dependence: root [2] T->Draw("Size:(Time-1000916452)") // while equivalent? ones gives very rough binning: root [4] T->Draw("Size:Time") root [5] T->Draw("Size:Time-1000916") There is probably some roundout problem .... Best regards Andrzej Kupsc --------------------------------------------------------------- Address : The Svedberg Laboratory, Uppsala University, Box 533, S-75121 Uppsala. Telephone : +46-18-4713439 Facsimile : +46-18-4713833 e-mail : kupsc@unix.tsl.uu.se --------------------------------------------------------------- On Wed, 19 Sep 2001, Rene Brun wrote: > Hi Andrzej, > > Currently, when a branch holds a variable of type integer, the histogram > created has an integer bin size. > However, the algorithm is not clever enough to recognize that Time-10008884 > is also an integer. As soon as an expression is used, the bin size is > assumed to be a float. > > You should create an histogram with the correct bin limits and bin size > before calling TTree::Draw, then do: > > tree->Draw("Time-10008884>>myhist"); > > Rene Brun > > Andrzej Kupsc wrote: > > > > Hi, > > In a tree I have a branch with C-time (secs>1970): > > > > tree->Branch("Time",&Time,"Time/i"); > > > > When I am plotting time vs other other variable say: > > tree->Draw("x:Time") > > The bins are much more coarse then in the case when time offset > > was subtraced: > > tree->Draw("x:(Time-1000883184)") > > > > There is not such big difference in automaticaly calculated bin > > size when one dimensional plot is requested: > > tree->Draw("Time") vs tree->Draw("Time-1000883184") > > > > I am using root 3.01/06 on RH7.0 > > > > Am I doing something wrong?
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