Re: Branches w/ different number of events

  > I want to create a root tree with 2 branches corresponding to 2 different  > analysis i.e. having different number of entries per branch. Is this possible?

Yes it is possible (just add tree->SetEntries(); before tree->Write()), __However__ It is strongly discouraged. Semantically your 2 branches have very little to do with each other and none of the automatically tools (TTree::Draw, TTree::Selector, browser, etc.) will be able to make good use of your TTree.

Instead we recommend that you simply create 2 different TTrees.

Cheers,
Philippe.

If there is a semantic link (like an event number) you can add this event number to each of the 2 trees and properly correlated them by making them friends (and creating an index on one of the two). An other alternative might be to use a collection of value (std::vector<float>) is 'bunches' of value from both analysis 'belongs' together.

On 9/1/10 2:42 PM, Hovhannes Khandanyan wrote:
> Dear ROOTers,
>
> I want to create a root tree with 2 branches corresponding to 2 different analysis i.e. having different number of entries per
> branch. Is this possible? The test macro below creates the required TTree structure, without filling the leaves though. What am I
> doing wrong?
>
> Thanks for any help,
> Hovhannes
>
> int test(){
> TFile* file = new TFile("myfile.root","recreate");
> TTree* tree = new TTree("T", "T");
>
> double var1, var2;
>
> tree->Branch("Ana1", &var1, "var1/F");
> tree->Branch("Ana2", &var2, "var2/F");
>
> for (int i = 10; i < 25; i++){
> var1 = i*2.45;
> TBranch* br1 = tree->GetBranch("Ana2");
> br1->Fill();
> }
>
>
>
> for (int i = 0; i < 5; i++){
> var2 = i*1.17;
> TBranch* br2 = tree->GetBranch("Ana2");
> br2->Fill();
> }
> tree->Write();
> file->Close();
>
> return 0;
> }
>
Received on Wed Sep 01 2010 - 22:03:27 CEST