Problem with fabs()

ROOT
1

Hello,

I have been trying to draw the contents of a root tree using xxxtree->Draw(“xxx”). However I would like to take the absolute value of the branches that I am drawing. I have found that if the branches are vectors then abs(xxx) works but fabs(xxxx) returns

Error in TTreeFormula::Compile: Bad numerical expression : “fabs(s_vxp_nTracks)”

where s_vxp_nTracks is a vector. Is there a way around this problem?

Alternatively, or in addition, is it possible to incorporate TCuts with the Fill command? Right now I am drawing histograms using xxxTree->Draw(“x:y”,*cuts); Is there a way to utilize TCuts in this manner but with Fill? For instance suppose I use MakeClass on a .root file and then, inside the event loop, I declare a histogram and use hist->Fill(x:y), could I incorporate the TCut into this?

Thank You

2

The 1st question: try
TMath::Abs(s_vxp_nTracks)
. As you know, sometimes abs() returns an integer.

The 2nd question:
I am not sure I well understand your question. But for me you may be able to use TEventList or TEntryList to do what you want.

root.cern.ch/root/html/TEventList.html

Cheers,
Zhiyi.