ROOT file bin thresh changed w/ IsVariabeBinSize(), but FindBin() still returning old thresh

[trenta_coollime]

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ROOT Version: 6.06.01
Platform: Ubuntu 16.04
Compiler: gcc530

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Hi, I recently changed the my root file’s hist’s Y axis() threshold from 20.0->12.0 with help of the two links below.

A way to extend the low bin edge of the lowest bin and save as .root file?

ROOT Version: 6_10 Platform: Ubuntu 16.04 Compiler: gcc 630 Hi, I have a rootfile, which has a 2D histogram with lowest bin (20,25). Is there an easy way to extend the lower threshold such that the bin has range of (12,25) with same bincontent? I guess one can literally use setbincontent, getbincontent functions for every single entry to recreate entire 2Dhist. However, I expect that experts would know a much faster shortcut for my situation where I need to change only one bin’s lower th…

VariableBinAxis Boolean True! but binning not getting fixed

ROOT Version: 6.14/06 Platform: Ubuntu 16.04 Compiler: 5.4.0 Hi, I have this root file attached, which contains 2D histograms. I want to change the Y-axis’s lowest binning to start from 12 instead of current 20. It is a variable bin that I checked with your_histogram->GetXaxis()->IsVariableBinSize() which gave me (bool) true So, I tried to change the lowest Y-bin to start from 12 instead of 20 with your_histogram->GetXaxis()->GetXbins()[0] = 12.; // the lowest edge but it gives me r…

Following the answers above with the code,

your_histogram->GetXaxis()->IsVariableBinSize()
(bool) true
(*(TArrayD*)NUM_LooseID_DEN_genTracks_eta_pt->GetYaxis()->GetXbins())[0] = 12.; 

for ROOT fileRunGH_SF_ID.root (16.2 KB), which changed into Run_SF_ID.root (15.7 KB).

When I look at the Second bin’s lower Edge with GetBinLowEdge(), It shows expected behavior with RunGH_SF_ID.root showing 20, Run_SF_ID.root showing 12.

root [3] NUM_LooseID_DEN_genTracks_eta_pt->GetYaxis()->GetBinLowEdge(1)
(Double_t) 12.0000

However, my code tries to get content of bin using this mechanism.

 Int_t tmpbinx       = your_histogram->GetXaxis()->FindBin( mueta );
   Int_t tmpbiny       = your_histogram->GetYaxis()->FindBin( mupt  );
   Int_t tmpbin        = your_histogram->GetBin( tmpbinx, tmpbiny );
   tmpweight = your_histogram-->GetBinContent(tmpbin);}

However, when I use the FindBin() function at 12.0 for Run_SF_ID.root, it gives me the value of 0 instead of 1, which is the supposed value for my hist w/ the new threshold.

root [2] NUM_LooseID_DEN_genTracks_eta_pt->GetYaxis()->FindBin(12)
(Int_t) 0

It returns the value of 1, only when it is above 20, which was the original threshold.
What is happening and how can I fix the bug?

Thank you!

[bellenot]

Maybe I’m mistaken, or @couet can give more details, but when drawing your histogram in 3D, it looks like the first bin (0) starts at 12 and ends at 20. Or did I miss something?

[Wile_E_Coyote]

You need to apply an additional fix:

// one must set the new proper "xmin" and "xmax" for this axis
NUM_LooseID_DEN_genTracks_eta_pt->GetYaxis()->SetLimits(
  (*NUM_LooseID_DEN_genTracks_eta_pt->GetYaxis()->GetXbins())[0],
  (*NUM_LooseID_DEN_genTracks_eta_pt->GetYaxis()->GetXbins())[NUM_LooseID_DEN_genTracks_eta_pt->GetNbinsY()]
);