doc/v606/transpad_8C.html

void transpad() {

   TCanvas *c1 = new TCanvas("c1","transparent pad",200,10,700,500);

   TPad *pad1 = new TPad("pad1","",0,0,1,1);

   TPad *pad2 = new TPad("pad2","",0,0,1,1);

   pad2->SetFillStyle(4000); //will be transparent

   pad1->Draw();

   pad1->cd();


   TH1F *h1 = new TH1F("h1","h1",100,-3,3);

   TH1F *h2 = new TH1F("h2","h2",100,-3,3);

   TRandom r;

   for (Int_t i=0;i<100000;i++) {

      Double_t x1 = r.Gaus(-1,0.5);

      Double_t x2 = r.Gaus(1,1.5);

      if (i <1000) h1->Fill(x1);

      h2->Fill(x2);

   }

   h1->Draw();

   pad1->Update(); //this will force the generation of the "stats" box

   TPaveStats *ps1 = (TPaveStats*)h1->GetListOfFunctions()->FindObject("stats");

   ps1->SetX1NDC(0.4); ps1->SetX2NDC(0.6);

   pad1->Modified();

   c1->cd();


   //compute the pad range with suitable margins

   Double_t ymin = 0;

   Double_t ymax = 2000;

   Double_t dy = (ymax-ymin)/0.8; //10 per cent margins top and bottom

   Double_t xmin = -3;

   Double_t xmax = 3;

   Double_t dx = (xmax-xmin)/0.8; //10 per cent margins left and right

   pad2->Range(xmin-0.1*dx,ymin-0.1*dy,xmax+0.1*dx,ymax+0.1*dy);

   pad2->Draw();

   pad2->cd();

   h2->SetLineColor(kRed);

   h2->Draw("][sames");

   pad2->Update();

   TPaveStats *ps2 = (TPaveStats*)h2->GetListOfFunctions()->FindObject("stats");

   ps2->SetX1NDC(0.65); ps2->SetX2NDC(0.85);

   ps2->SetTextColor(kRed);


   // draw axis on the right side of the pad

   TGaxis *axis = new TGaxis(xmax,ymin,xmax,ymax,ymin,ymax,50510,"+L");

   axis->SetLabelColor(kRed);

   axis->Draw();

}