データ型の変換

TGraph → TH1

TGraph* g1 = new TGraph();
  :
TH1F* h1 = g1->GetHistogram();

TF1 → TGraph

TF1* f1 = new TF1();
  :
TGraph* g1 = new TGraph(f1);

TGraph2D → TH2

TGraph2D* g2 = new TGraph2D();
  :
TH2D* h2 = g2->GetHistogram();