/* Root Macro to Produce a Linear Fit on 6 DAC Outputs */
/*      and Display all 6 Graphs in One Canvas         */

Double_t func(Double_t*x,Double_t*par)                                         
{                                                                              
  Double_t xx=x[0];                                                    
  if (xx<=0) return 0;                                          
  return par[0]*xx+par[1]; 
}

void plot()
{    
   TF1 *lin = new TF1("lin",func,0,255,2);    // x in [0;255], 2 parameters 
   lin->SetParName(0,"Gradient");
   lin->SetParName(1,"Offset");                                                  

   Int_t regvalue, counter = 0;
   const Int_t  n = 256;       //256 data points per graph
   Double_t a,b,c,x,y,z;
   Double_t par[12];           //2 parameters * 6 DACS
   Double_t val[n];
   Double_t dac1[n], dac2[n], dac3[n], dac4[n], dac5[n], dac6[n];
   ofstream dataout("fit_pars.txt");

   /* Input Data */
   char* dac_name[] = {"TESTLOW", "TESTHI", "GTLA", "GTLD", "DRMID", "DRHI"}; 
   ifstream in;
   in.open("data.txt");
   for(Int_t i=0; i<n; i++){
     in>>regvalue>>a>>b>>c>>x>>y>>z;
     if(!in.good()) break;
     val[i] = regvalue;
     dac1[i] = a;
     dac2[i] = b;
     dac3[i] = c;
     dac4[i] = x;
     dac5[i] = y;
     dac6[i] = z;
     counter++;
   }
   in.close();

   cout<<"Counter: "<<counter<<endl;

/* Create canvas and divide into 6 */
   TCanvas *cc = new TCanvas("cc","Canvas",1200,800);   
   cc->Divide(3,2,0,0);

/* Create 6 TGraphs for the 6 DAC plots */
   TGraph *d1 = new TGraph(n, val, dac1);
   TGraph *d2 = new TGraph(n, val, dac2);
   TGraph *d3 = new TGraph(n, val, dac3);
   TGraph *d4 = new TGraph(n, val, dac4);
   TGraph *d5 = new TGraph(n, val, dac5);
   TGraph *d6 = new TGraph(n, val, dac6);
   
/* Set Fit Conditions */
   lin->SetParameter(0,3);
   lin->SetParameter(1,1);
   lin->SetLineWidth(2);
   lin->SetLineColor(2);

/* DAC 1 */
   d1->SetLineWidth(2);
   d1->SetTitle("TESTLOW");
   d1->GetXaxis()->SetTitle("DAC Register Value");
   d1->GetYaxis()->SetTitle("Output Voltage V");
   d1->GetXaxis()->CenterTitle();
   d1->GetYaxis()->CenterTitle();
   d1->GetYaxis()->SetTitleOffset(1.5);
   d1->Fit("lin","R");
   lin->GetParameters(&par[0]);

/* DAC 2 */
   d2->SetTitle("TESTHI");
   d2->GetXaxis()->SetTitle("DAC Register Value");
   d2->GetYaxis()->SetTitle("Output Voltage V");
   d2->GetXaxis()->CenterTitle();
   d2->GetYaxis()->CenterTitle();
   d2->GetYaxis()->SetTitleOffset(1.5);
   d2->Fit("lin","R");
   d2->SetLineWidth(2);
   lin->GetParameters(&par[2]);

/* DAC 3 */
   d3->SetTitle("GTLA");
   d3->GetXaxis()->SetTitle("DAC Register Value");
   d3->GetYaxis()->SetTitle("Output Voltage V");
   d3->GetXaxis()->CenterTitle();
   d3->GetYaxis()->CenterTitle();
   d3->GetYaxis()->SetTitleOffset(1.5);
   d3->Fit("lin","R");
   d3->SetLineWidth(2);
   lin->GetParameters(&par[4]);

/* DAC 4 */
   d4->SetTitle("GTLD");
   d4->GetXaxis()->SetTitle("DAC Register Value");
   d4->GetYaxis()->SetTitle("Output Voltage V");
   d4->GetXaxis()->CenterTitle();
   d4->GetYaxis()->CenterTitle();
   d4->GetYaxis()->SetTitleOffset(1.5);
   d4->Fit("lin","R");
   d4->SetLineWidth(2);
   lin->GetParameters(&par[6]);

/* DAC 5 */
   d5->SetTitle("DRMID");
   d5->GetXaxis()->SetTitle("DAC Register Value");
   d5->GetYaxis()->SetTitle("Output Voltage V");
   d5->GetXaxis()->CenterTitle();
   d5->GetYaxis()->CenterTitle();
   d5->GetYaxis()->SetTitleOffset(1.5);
   d5->Fit("lin","R");
   d5->SetLineWidth(2);
   lin->GetParameters(&par[8]);

/* DAC 6 */
   d6->SetTitle("DRHI");
   d6->GetXaxis()->SetTitle("DAC Register Value");
   d6->GetYaxis()->SetTitle("Output Voltage V");
   d6->GetXaxis()->CenterTitle();
   d6->GetYaxis()->CenterTitle();
   d6->GetYaxis()->SetTitleOffset(1.5);
   d6->Fit("lin","R");
   d6->SetLineWidth(2);
   lin->GetParameters(&par[10]);

/* Insert Graphs into Canvas */
   gStyle->SetOptFit(0001);
   cc->cd(1);
   d1->Draw("AC+");
   cc->cd(2);
   d2->Draw("AC+");
   cc->cd(3);
   d3->Draw("AC+");
   cc->cd(4);
   d4->Draw("AC+");
   cc->cd(5);
   d5->Draw("AC+");
   cc->cd(6);
   d6->Draw("AC+");

   cc->Update();

/* Write Fit Parameters to File */
   dataout<<"DAC"<<'\t'<<"Gradient"<<'\t'<<"Offset"<<endl;
   for(Int_t j=0; j<6; j++)
     {
       Int_t k = 2*j;
       dataout<<dac_name[j]<<'\t'<<par[k]<<'\t'<<par[k+1]<<endl;
       }                                                       
}