void focus() {
  gROOT->SetStyle("Plain");

  TCanvas *c1;
  c1=new TCanvas("c1","Canvas",800,600);

  //gPad->SetPadLeftMargin(1);
  gStyle->SetPadLeftMargin(0.12);
  c1->UseCurrentStyle();
  //gROOT->ForceStyle();

  const unsigned ne(11);
  double e[ne]={17,74,155,197,202,169,186,157,97,47,35};
  double x[ne]={-0.2,-0.1,0.0,0.05,0.075,0.1,0.1,0.15,0.2,0.25,0.3};

  TGraph *tg;
  tg=new TGraph(ne);
  tg->SetTitle(";Optical focus reading (mm);Laser signal (DTU)");

  for(int j(0);j<(int)ne;j++) {
    tg->SetPoint(j,x[j],e[j]);
  }
    
  tg->SetMarkerStyle(20);
  tg->SetMarkerSize(1.5);
  tg->SetMarkerColor(2);
  tg->SetLineColor(2);
    
  //tg->GetYaxis()->SetRangeUser(0,15);
  //tg->GetXaxis()->SetRangeUser(-0.4,0.5);
  tg->GetXaxis()->SetLimits(-0.3,0.4);
  tg->GetYaxis()->SetTitleOffset(1.2);
    
  tg->Draw("AP");
    
  c1->Update();
  c1->Print("../focus.png");
}