void sipm_plotHVsetting(void)
{
// 
// Input the .csv data file from excel file into arrays for processing.
//

//#include <TMath.h>
#include <TRandom.h>
#include <TTree.h>

gROOT->Reset();
//TTree *Bfield = (TTree *) gROOT->FindObject("Bfield");
//gROOT->LoadMacro("$ROOTSYS/test/libEvent.so"); 
gStyle->SetPalette(1,0);
gStyle->SetOptStat(kFALSE);
// gStyle->SetOptFit(kFALSE);
gStyle->SetOptFit(1111);
gStyle->SetPadRightMargin(0.15);
gStyle->SetPadLeftMargin(0.15);
gStyle->SetPadBottomMargin(0.15);
gStyle->SetFillColor(0);
//

   char line[1024];
   char filename[132];
   char name[10];
   Double_t pi=3.14159;
   Int_t j,jj;
   
   sprintf(filename,"%s","9-20-2011_302.csv");
   printf ("Read from filename=%s\n",filename);
   ifstream in1 (filename);

   # define npts 6;   
   Double_t HVps[npts]={78.9,78.3,78.0,77.3,76.8,76.5};
   Double_t HVsipm[npts]={72.4,71.8,71.5,70.9,70.4,70.1};

   Double_t xmin=75;
   Double_t xmax=80; 
   Double_t ymin=70;
   Double_t ymax=73;

   //
   TCanvas *c1 = new TCanvas("c1","c1 sipm_plotHVsetting Canvas",200,10,700,700);
   c1->SetBorderMode(0);
   c1->SetFillColor(0);
   c1->SetGridx();
   c1->SetGridy();

   TGraph *hvplot = new TGraph (npts,HVps,HVsipm);
   /*t1 = new TLatex(0.5,0.8,string);
   t1->SetTextColor(1);
   t1->SetNDC();
   t1->Draw();*/

   hvplot->SetTitle("");
   hvplot->GetXaxis()->SetRangeUser(xmin,xmax);
   hvplot->GetYaxis()->SetRangeUser(ymin,ymax);
   hvplot->GetXaxis()->SetTitleSize(0.05);
   hvplot->GetYaxis()->SetTitleSize(0.05);
   hvplot->GetYaxis()->SetTitleOffset(1.5);
   hvplot->GetYaxis()->SetTitle("SiPM Voltage (V)");
   hvplot->GetXaxis()->SetTitle("Power Supply Voltage (V)");
   hvplot->GetXaxis()->SetNdivisions(5);
   hvplot->SetMarkerColor(2);
   hvplot->SetMarkerStyle(20);
   hvplot->SetMarkerSize(2);
   hvplot->Draw("AP");

  Double_t fitmin=xmin;
  Double_t fitmax=xmax;
  hvplot->Fit("pol1","","",fitmin,fitmax);



  c1->SaveAs("sipm_plotHVsetting_c1.pdf");


  // close input file
}