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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