Hi Andrzej, OK, I see the problem now. This is a precision problem due to the fact that the class TPolyMarker uses single precision. I have modified this class to use double precision for the storage of the points. The fix is in CVS. Rene Brun On Wed, 19 Sep 2001, Andrzej Kupsc wrote: > 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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