Issue with TTree::Draw and Conditional Branch Selection

[ficov12960]

Hey guys…

I am currently working on analyzing a ROOT file containing a large TTree with multiple branches, and I am running into some trouble when using the TTree::Draw method with conditional branch selection.

Specifically, I need to apply a condition to select events where one branch (let’s call it BranchA) satisfies a specific range, and then plot the corresponding values of another branch (BranchB). Here’s a simplified version of the code I’m using:

TFile* file = TFile::Open("data.root");  
TTree* tree = (TTree*)file->Get("myTree");  
tree->Draw("BranchB", "BranchA > 10 && BranchA < 50");  

While this works for some of my datasets, I occasionally encounter unexpected results—plots that appear empty even though I know the condition is satisfied for several entries. I’ve double-checked the branch names and values in the TTree Viewer, and everything seems fine.

I have not found any solution. Has anyone else experienced similar issues? Could it be related to the way the branches are stored or some internal optimization in TTree::Draw? Any advice on debugging this further or alternative approaches would be greatly appreciated.

Thanks in advance!

[dastudillo]

@ficov12960

I know the condition is satisfied for several entries

How exactly do you know? For example, does

tree->Scan("BranchB", "BranchA > 10 && BranchA < 50"); 

give you entries while

tree->Draw("BranchB", "BranchA > 10 && BranchA < 50"); 

doesn’t? If this is the case, check in detail the events that Scan shows but Draw doesn’t, maybe there’s some issue with the tree.

[pcanal]

Another idea is to look at the result of:

tree->Scan(tBranchB:BranchA:BranchA>10:BranchA<50:BranchA > 10 && BranchA < 50");