#include <vector>

void peak_study(Double_t pedestal=100)
{

gROOT->Reset();
//TTree *Bfield = (TTree *) gROOT->FindObject("Bfield");
gStyle->SetPalette(1,0);
gStyle->SetOptStat(kTRUE);
gStyle->SetOptFit(kTRUE);
gStyle->SetOptFit(1111);
gStyle->SetPadRightMargin(0.15);
gStyle->SetPadLeftMargin(0.15);
gStyle->SetPadBottomMargin(0.15); 

gStyle->SetLabelSize(0.05,"XYZ");
gStyle->SetTitleSize(0.05,"XYZ");
gStyle->SetTitleOffset(1.5,"Y");
gStyle->SetNdivisions(505,"XYZ");

// gStyle->SetFillColor(0);
//
   char string[256];
   const int npts=3;

   // Double_t pedestal=100;
   Double_t ped_sigma=1.2;

  TF1 *p2 = new TF1("p2","pol2",-2,2);
  p2 ->SetParameters(50,5,-10);

  // data from function

  Double_t x[npts];
  Double_t y[npts];

  for (Int_t jj=0;jj<npts;jj++) {
      x[jj] = jj-1;
      y[jj] = p2->Eval(x[jj]);
     }

  TGraph *points = new TGraph(npts,x,y);

   // compute maximum


  Double_t x_peak = -0.5 * (y[2]-y[0])/(y[0]-2*y[1]+y[2]);
  Double_t y_peak = y[1] - (y[2]-y[0])*(y[2]-y[0])/(y[0]-2*y[1]+y[2])/8;

  cout << "x_peak=" << x_peak << " y_peak=" << y_peak << endl;

  TMarker *peak = new TMarker(x_peak, y_peak,21);

   TCanvas *c1 = new TCanvas("c1", "c1",200,10,700,700);
   // c1->Divide(1,2);
   c1->SetGridx();
   c1->SetGridy();
   // c1->SetLogx();

   // ouput legend

   TLegend *leg = new TLegend(0.25,0.7,0.55,0.9);

   p2->Draw();
   p2->SetLineColor(1);
   points->SetMarkerStyle(20);
   points->SetMarkerColor(4);
   points->SetMarkerSize(1);
   points->Draw("psame");

   peak->SetMarkerColor(2);
   peak->SetMarkerSize(1.2);
   peak->Draw("psame");

   //leg->Draw();


   /*sprintf (string,"Effect of correlations on average \n");
   printf("string=%s",string);
   t1 = new TLatex(0.15,0.92,string);
   t1->SetNDC();
   t1->SetTextSize(0.03);
   t1->Draw();*/

   sprintf (string,"peak_study_%04d.pdf)",pedestal*10);
   c1->SaveAs(string);
   sprintf (string,"peak_study_%04d.png",pedestal*10);
   c1->SaveAs(string);



}
Double_t sqrt_func (Double_t *x, Double_t *par) {

   Double_t sigma1=par[0];
   Double_t x1=x[0];

   char string[256];

   Double_t func;

   func = sigma1/sqrt(x1);

   return func;
}