How can I access the object appended to another object

ROOT
1

How can I access the object afterword which is appended to another object? Following examle appended TGraph object tg was appended
to testhist object. I would like to access TGraph object afterword when
I open the test.root.

main(){

TFile * rootfile = new TFile(“test.root”,“RECREATE”,“ROOT Histogram file”);

TH2F * testhist = new TH2F(“testhist”,“test histo”,100,-1,1, 100,-10,10);
TGraph * tg = TGraph(N,x,y);
testhist->GetListOfFunctions()->Add(“tg”);

rootfile->Write();
rootfile->Close();

}

root [] TFile * file = TFile::Open(“test.root”);
root [] testhist->GetListOfFunctions() -> FindObject(“tg”);

seems doesn’t work.

2

You should do instead:

TH2F * testhist = new TH2F("testhist","test histo",100,-1,1, 100,-10,10); TGraph * tg = TGraph(N,x,y); tg->SetName("tg"); testhist->GetListOfFunctions()->Add(tg);

3

int
main(){

Float_t x[5]={1,2,3,4,5};
Float_t y[5]={10,20,30,40,50};

TFile * rootfile = new TFile(“test.root”,“RECREATE”,“ROOT Histogram file”);
TH1F * testhist = new TH1F(“testhist”,“test histo”,100,-10,10);
TGraph* tg = new TGraph(5,x,y);
tg->SetName(“tg”);

testhist->GetListOfFunctions()->Add(tg);

rootfile->Write();
rootfile->Close();

return 0;

}

root [] TFile * file = TFile::Open(“test.root”);
root [] TGraph * tmp = (TGraph*) testhist -> GetListOfFunctions()->FindObject(“tg”);
root [] Float_t * y = tmp->GetY();
root [] cout << y[0] << " " << y[1] << " " << y[2] …
0 0.1875 0 2 …

Somehow I still cannot access to the right address to reproduce contents
of arrays.

4

The TGraph constructors accept float* and double* arrays, but internally
they are stored as double only.
So, in your reading session, replace

Float_t *y=tmp->GetY();by

Rene