Opening a histogram from a file

[Wile_E_Coyote]

Execute the following and post the output here:
TFile *f = TFile::Open(“first_file.root”);
f->ls();
c1->Draw();
c1->GetListOfPrimitives()->Print();

See also, for example:

Error fitting Histo from a Canvas

TFile miofile(“test.root”); TCanvas can = (TCanvas)miofile.Get(“c1”); TH1D his = ((TH1D)(can->FindObject(“MCA”))); Double_t xmin = his->GetBinCenter(1); Double_t xmax = his->GetBinCenter(his->GetNbinsX()); his->Fit(“gaus”, “”, “”, xmin, xmax); can->Draw(); TFile miofile(“test.root”); TCanvas can = (TCanvas)miofile.Get(“c1”); ((TPad *)can->FindObject(“pad1”))->GetListOfPrimitives()->ls(); ((TPad *)can->FindObject(“pad1”))->GetListOfPrimitives()->Print(); TH1D his = ((TH1D)(((TPad *)can…

Problem with accessing histogram from canvas

If your histogram resides in any sub-pad, it will NOT be found by “canvas->GetPrimitive(…)”. For some solutions see here (the “MCA” resides in the “pad1”): [url]Error fitting Histo from a Canvas

How to adjust range in canvas?

I’m afraid each canvas / pad will have a different name for its “frame” histogram and so you need to play a bit with the TList returned by the “TList *l = c->GetListOfPrimitives();” in order to find it (for example, find the first key which name begins with “frame_” or maybe it’s sufficient to find the first key which is a TH1D or maybe it’s simply always the second key in the list). Your attached “file.root” has a “frame_2a3b440”. [code]#include “TFile.h” #include “TCanvas.h” #include “TH1.h…

Getting TGraph from TChain

TGraph *g = ((TGraph *)((c.GetPrimitive(“Graph”)).Clone(“MyNewGraph”))); TGraph *g = ((TGraph *)((c.FindObject(“Graph”)).Clone(“MyNewGraph”)));