{
   gROOT->Reset();

   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);  
       //       printf("%d %f\n", in, y2[in]);
   }
   
   // Create 2 normal tgraphs
   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","my pad 1",0,0,1,1);
   TPad *pad2 = new TPad("pad2","my pad 2",0,0,1,1);
   pad2->SetFillStyle(4000); //will be transparent
   pad1->Draw();
   pad1->cd();

   
   // Draw the first graph with axis (A) and  Smooth Curve (C) 
   inputSpec->Draw("AC");
   gPad->Update();


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

   pad2->Draw();
   pad2->cd();
   
   inputSpec2->SetLineColor(kRed);
   // Smooth curve (C) with Marker (P), try AY+
   // AY+ clears the previous graph
   inputSpec2->Draw("CP");

   Double_t pad1x[2], pad1rax[2];
   Double_t xy[4];
   pad1->GetRange(xy[0], xy[1], xy[2], xy[3]);
   pad1x[0] = xy[0];
   pad1x[1] = xy[2];
   printf("pad1 Range = %f %f %f %f\n", xy[0],xy[1],xy[2],xy[3]);
   pad1->GetRangeAxis(xy[0],xy[1],xy[2],xy[3]);
   pad1rax[0] =  xy[0];
   pad1rax[1] =  xy[2];
   printf("pad1 RangeAxis = %f %f %f %f\n", xy[0],xy[1],xy[2],xy[3]);

      // Set values;
   printf("%f %f\n", pad1x[0], pad1x[1]);
   //compute the pad range with suitable margins
   Double_t ymin = 0;
   Double_t ymax = 0.5;
   Double_t dy = (ymax-ymin)/0.8; //10 per cent margins top and bottom
   //   pad2->Range(xmin-0.1*dx,ymin-0.1*dy,xmax+0.1*dx,ymax+0.1*dy);
   pad2->Range( pad1x[0], ymin-0.1*dy, pad1x[1], ymax+0.1*dy);
   pad2->RangeAxis( pad1rax[0], 0.0, pad1rax[1], 0.5);
   pad2->Update();

   pad2->GetRange(xy[0],xy[1],xy[2],xy[3]);
   printf("pad2 Range = %f %f %f %f\n", xy[0],xy[1],xy[2],xy[3]);
   pad2->GetRangeAxis(xy[0],xy[1],xy[2],xy[3]);
   printf("pad2 RangeAxis = %f %f %f %f\n", xy[0],xy[1],xy[2],xy[3]);


   //draw an axis on the right side
   // Use the size of the pad as the first 4 arguments. 
   // xmin, ymin, xmax, ymax
   // wmin, wmax, ndiv, chopt
   //   wmin - XOrigin in WC space
   //   wmax - XEnd in WC space
   //   ndiv = N1 + 100*N2 + 10000*N3
   //       where N1 = number of 1st divisions
   //             N2 = number of second divisions
   //             N3 = number of thrid divisions. 
   //       eg in this case 5 third divisions, 1 second and zero first.
   // 
   // +L - (+) draw tick marks on positive side.
   //      (L) labels are left justified
   //  
   TGaxis *axis = new TGaxis(gPad->GetUxmax(),
                             gPad->GetUymin(),
                             gPad->GetUxmax(),
                             gPad->GetUymax(),
                             0,0.5,510,"+L");

    axis->SetLineColor(kRed);
    axis->SetTextColor(kRed);
    axis->Draw("G");
}