Axis label disappears on saving

[Adam_Hunyadi]

Hey there,

I have been wasting a lot of time trying to change the labels on the histograms I create and save to an ntuple, but I always failed. Upon checking this simple root script, I realized, that even this simple script fails:

root [0] TH1D a("a", "a", 100, 0, 100)
(TH1D &) Name: a Title: a NbinsX: 100
root [1] a.GetXaxis() -> ChangeLabel(1, -1, 0.025, -1, -1, -1, "alma");
root [2] a.SaveAs("a.C")
Info in <TH1D::SaveAs>: C++ Macro file: a.C has been generated
root [3] a.GetXaxis() -> GetBinLabel(1)
(const char *) ""
root [4] a.Draw("") // Only this shows the correct label
Info in <TCanvas::MakeDefCanvas>:  created default TCanvas with name c1

More importantly, this fails too:

root [0] TH1D a("a", "a", 100, 0, 100)
(TH1D &) Name: a Title: a NbinsX: 100
root [1] a.GetXaxis() -> ChangeLabel(1, -1, 0.025, -1, -1, -1, "alma");
root [2] TFile::Open("alma.root", "RECREATE")
(TFile *) 0x2eb6a40
root [3] a.Write()
(Int_t) 301

I want to save my histograms with the correct labels, but the SaveAs() seem to fail achieving this. What am I doing wrong?
My root version is ROOT 6.08/02.

Cheers,
Hunyadi Adam

[couet]

I think it is simply not implemented when you save the pad a a .C file. Other formats are ok.

[Adam_Hunyadi]

I don’t really want to save a histogram as .C. However, I need to write histograms with modified labels to an Ntuple. How can I do it properly?

[couet]

As I said some implementation is missing. That’s a new feature and It might be that something are missing. I will look at it.

[couet]

The following macro illustrate the problem. On the left the original histogram with changed label and the number of division also changed. On the right the histogram retrieved from file . I am investigating.

void changelabelsave(){
   auto a = new TH1D("a", "a", 100, 0, 1);
   a->GetXaxis()->SetNdivisions(5);
   a->GetXaxis()->ChangeLabel(1, -1, 0.025, -1, -1, -1, "Changed Label");

   auto c= new TCanvas();
   c->Divide(2,1);
   c->cd(1);
   a->Draw();

   TFile *f1 = new TFile("a.root","RECREATE");
   a->Write();
   f1->Close();

   TFile *f2 = new TFile("a.root","READ");
   auto b = (TH1D*)f2->Get("a");
   c->cd(2);
   b->Draw();
}

[couet]

Problem now fixed in ROOT master. Thanks to have seen it.