try this simple script:
{
TH1F h1;
h1.SetName("h1");
h1.Fill("10", 1);
TFile f1("f1.root", "RECREATE");
h1.Write();
h1.Reset();
h1.Fill("20", 1);
TFile f2("f2.root", "RECREATE");
h1.Write();
}
now:
hadd f.root f1.root f2.root
everythigs works, the new histograms has 2 bins, the first is labelled “10”, the second “20” and the entries are 2.
Now use TH2F instead:
{
TH2F h1;
h1.SetName("h1");
h1.Fill("10", "a", 1);
TFile f1("f1.root", "RECREATE");
h1.Write();
TH2F h2; // Reset doesn't work!!! I need to use another variable
h2.SetName("h1");
h2.Fill("20", "a", 1);
TFile f2("f2.root", "RECREATE");
h2.Write();
}
now add the to files, but the final histograms has only one bin on the x axis labelled as “10” and 2 entries. I think this is wrong.