{
   const Int_t N = 10;
   Int_t NMax, in;
   Float_t x[N], y1[N], y2[N], x1, step, dir;

   y1[0] = 5.0;
   y2[0] = 0.1;
   step  = 0.5;
   x[0]  = 0.0;

   for (in=1; in<N; in++) {
      if (in<N/2) dir = -1.0;
      else dir = 1.0;
      x[in]  = (Float_t) in;
      y1[in] = y1[in-1]+(2.0*step*dir);
      y2[in] = y2[in-1]+(-0.1*step*dir);  
   }
   
   TGraph *inputSpec  = new TGraph(N, x, y1);
   TGraph *inputSpec2 = new TGraph(N, x, y2);

   TH1F *h1 = inputSpec->GetHistogram();
   h1->Scale(0.1);
   h1->SetXTitle("X title");
   h1->SetYTitle("Y title");
   
   TCanvas *c1 = new TCanvas("c1", "Intensity of LED 1",0,  0, 800, 600); 
   TPad *pad1 = new TPad("pad1","",0,0,1,1);
   TPad *pad2 = new TPad("pad2","",0,0,1,1);
   pad2->SetFillStyle(4000);    // Makes pad2
   pad2->SetFrameFillStyle(0);  // transparent.

   pad1->Draw();
   pad1->cd();
   
   inputSpec->Draw("AC");

   TH1F *h2 = inputSpec2->GetHistogram();
   TAxis *Ay2 = h2->GetYaxis();
   Ay2->SetRangeUser(0.0, 0.5);

   pad2->Draw();
   pad2->cd();
   
   inputSpec2->SetLineColor(kRed);
   inputSpec2->Draw("CPAY+");
}