latour
February 22, 2005, 6:31pm
1
HI dear rooters,
I am a root beginner and I have a problem when trying to histogram the content of a variable in a branch. I finished by using the same code as the one in tree2.C of the tutorial, but it still does not work.
void treemanu2(){ntp999 = (TTree )f->Get(“ntp999”);
The m_mes variable does not contain the supposed values (that would be around 5.275) but very large floats:
Axel
February 22, 2005, 9:55pm
2
Hi latour,static Float_t m_mes;
Float_t* p_mes=&m_mes;
bm_mes->SetAddress(&p_mes); should work. It might also be that the branch stores a Double_t, and not a Float_t - if the above doesn’t help please tell us how you created and filled the branch; the output of bm_mes->Print() would then also be interesting to see.
latour
February 23, 2005, 11:36am
3
Hi Axel,
First, thank you for your quick answer.
I tried replacing Float_t by Double_t but the result is the same.
Concerning the creation of the branch, I am a bit puzzled: it is actually one of the numerous branch of an ntuple that was generated by a method from the C++ BaBar code. Each column of the ntuple is written by:
When I use the bm_mes->Print():
void treemanu2(){
TFile *f=new TFile ("generic/ccbar/prod3/Dstar0CPK_ccbar-Run4-29.root");
TTree *ntp999 = (TTree*)f->Get("ntp999");
static Float_t m_mes;
Float_t* p_mes=&m_mes;
TBranch *bm_mes=ntp999->GetBranch("m_mes");
bm_mes->SetAddress(&p_mes);
bm_mes->Print();
TH1F *hmes = new TH1F("hmes","Mes",100,-5.273,5.283);
Int_t nentries = (Int_t)ntp999->GetEntries();
for (Int_t i=0;i<nentries;i++) {
cout << "i=" << i << endl;
bm_mes->GetEntry(i);
bm_mes->Print();
cout <<"mes=" <<m_mes << endl;
hmes->Fill(m_mes);
}
}
I get:
Does it help? Thank you in advance.
pcanal
February 23, 2005, 3:04pm
4
Hi,
The problem is that in your tree there is no way to distinguish any of the branches (they all have the same name). If this was intentional, then you might know which branch you need by its index. You could use tree->GetListOfBranches()
Cheers,
Axel
February 23, 2005, 4:05pm
5
…and your branches contain a Double_t, not a Float_t.
latour
February 23, 2005, 5:03pm
6
I do not really understand: I just have one branch called m_mes (the other branches have different name), which contains the mes values for all my events. So what do you mean by all the branches have the same name?
Axel
February 23, 2005, 5:15pm
7
Hi Emmanuel,after the “for (Int_t i=0;i<nentries;i++)” loop, i.e. right before the method’s closing “}”?
Did you fix your code to use a Double_t instead of a Float_t?
latour
February 23, 2005, 5:45pm
8
The output is the following (I quoted what we are interested in):
*Tree :ntp999 : Denis Ntuple *
*Br 0 :m_runnumber : m_runnumber/I *… … … … … … … … … … … … … … … … … … … … … … … … … …
*Br 27 :m_mes_fit : m_mes_fit/D *… … … … … … … … … … … … … … … … … … … … … … … … … … … … … … … … … … … … … … … … … … … … … … … … … … … … … … … … … … … … … … … … … … … … … … … … … … … … … … … … … … … …
Sorry for bothering you with this.
latour
February 23, 2005, 5:46pm
9
And I changed Float_t to Double_t: does not change anything.
Axel
February 23, 2005, 8:47pm
10
Hi Emmanuel,
latour
February 24, 2005, 9:54am
11
Hi Axel,
void treemanu2(){
TFile *f=new TFile ("generic/ccbar/prod3/Dstar0CPK_ccbar-Run4-29.root");
TTree *ntp999 = (TTree*)f->Get("ntp999");
static Double_t m_mes;
Double_t* p_mes=&m_mes;
TBranch *bm_mes=ntp999->GetBranch("m_mes");
bm_mes->SetAddress(&p_mes);
//bm_mes->Print();
TH1F *hmes = new TH1F("hmes","Mes",100,-5.273,5.283);
Int_t nentries = (Int_t)ntp999->GetEntries();
for (Int_t i=0;i<nentries;i++) {
cout << "i=" << i << endl;
bm_mes->GetEntry(i);
// bm_mes->Print();
// cout <<"mes=" <<m_mes << endl;
hmes->Fill(m_mes);
}
ntp999->Print();
}
Axel
February 24, 2005, 5:42pm
12
Hi Emmanuel,treemanu2.C (519 Bytes)
latour
February 25, 2005, 10:45am
13
Thanks a lot for help.