Warning from TH1 Add about different axis limits

ROOT
1

Dear ROOTers,

I am having a strange issue with ROOT 5.22/00d and I wonder if I should worry about it at all… Here it is.

I create histograms in a separate piece of code, for example using this command:

TH1D *jpsi_eta_loose = new TH1D ("jpsi_eta_loose","jpsi_eta_loose",540,-2.7,2.7);

Then this histogram is filled and saved to a TFile.

Later on, I read the TFile and I do the following:

TH1D* eta_a_l_h = new TH1D("eta_a_l_h","",540,-2.7,2.7);
eta_a_l_h->Add(jpsi_eta_loose);

and that’s where ROOT gives me a warning:

Warning in TH1D::Add: Attempt to add histograms with different axis limits

Strangely, I get it only for TH1’s where the xmin and xmax are not integer values.

About this, I have two questions:

  • Why is ROOT complaining, since both histo have been created with the same command?
  • Should I be worried about this, or should this warning be ignored simply? Still, would be nice to understand it.

Thanks in advance,

Andrée