Double_t myFuncBWG(Double_t *x, Double_t *par)
   {
      Float_t xx =x[0];
      Double_t f=0.;
      Double_t a = 1.;

          if(xx>0.){
            a=TMath::Sqrt(xx/par[1]);
	  }
     f = par[0]*TMath::Voigt(xx-par[1],par[2],par[3]*a,4);    
    
   return f;
   }

//========================================================



void Voigtfun(){
  
  
 
  double par[4] = {25,0.2,.1,0.2}; //{A,mean,sigma,Gamma}
  

  
  
  
  
    f1 = new TF1("f1",myFuncBWG,-10,10,4);
  f1->SetParameters(&par[0]);
  f1->SetNpx(1000);
   f1->SetLineColor(2); 
   f1->SetLineWidth(3); 
   
  
  TH2F *h = new TH2F("h","h",200,-1,2,1000,0,120);
 h->SetTitle(0);
h->SetStats(0);
h->SetXTitle("E^{*} MeV");
h->SetYTitle("Counts");
h->SetLabelFont(22,"X");
h->SetLabelFont(22,"Y");
h->SetTitleFont(22,"X");
h->SetTitleFont(22,"Y");
h->GetXaxis()->CenterTitle();
h->GetYaxis()->CenterTitle();
h->GetXaxis()->SetTitleSize(0.05);
h->GetYaxis()->SetTitleSize(0.05);
h->GetXaxis()->SetTitleOffset(.8);
h->GetYaxis()->SetTitleOffset(.8);


  
  TCanvas *c = new TCanvas("c","c",800,800);
  
  c->cd();
  h->Draw();


  f1->Draw("same");  
  
  
  
  
  
  
}