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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