void drawSystErrors(TH1* h, Float_t err, Int_t style=0, 
                    Int_t color=16) 
{
  // cap sizes
  Float_t dx = 0.03;
  Float_t dy = 0.006;

  TGraph* band1 = new TGraph();
  TGraph* band2 = new TGraph();
  Int_t p=0;

  for (Int_t b=1; b<h->GetNbinsX(); b++) {
    Float_t w = h->GetBinWidth(b);
    Float_t x = h->GetBinCenter(b);
    Float_t y = h->GetBinContent(b);
    Float_t ye = h->GetBinError(b);

    Float_t x1 = x+dx;
    Float_t x2 = x-dx;
    Float_t y1 = y+TMath::Sqrt(ye*ye + y*err*y*err);
    Float_t y2 = y-TMath::Sqrt(ye*ye + y*err*y*err);

    if (ye==0 && y==0) continue;

    // boxes
    if (style==0||style==1) {
      TBox* box;
      if(style==0)
        box = new TBox(x-0.5*w,y+y*err,x+0.5*w,y-y*err);
      box->SetFillColor(color);
      box->SetLineColor(color);
      box->SetFillStyle(1001);
      box->Draw();

    }
    // caps
    if (style==2) { 
      TLine* lu = new TLine(x1,y1,x2,y1);
      TLine* ll = new TLine(x1,y2,x2,y2);
      lu->Draw();
      ll->Draw();
      
      TLine* lu1 = new TLine(x1,y1,x1,y1-dy);
      TLine* lu2 = new TLine(x2,y1,x2,y1-dy);
      lu1->Draw();
      lu2->Draw();
      
      TLine* ll1 = new TLine(x1,y2,x1,y2+dy);
      TLine* ll2 = new TLine(x2,y2,x2,y2+dy);
      ll1->Draw();
      ll2->Draw();
    }
    // bands
    if (style==3||style==4) {
      band1->SetPoint(p,x,y1);
      band2->SetPoint(p,x,y2);
      p++;
    }
  }
  if (style==3||style==4) {
    
    band1->SetLineColor(color);
    band2->SetLineColor(color);
    band1->SetFillColor(color);
    band2->SetFillColor(color);

    TGraph* band= new TGraph(2*p);
    band->SetLineColor(color);
    band->SetFillColor(color);
    for (Int_t i=0; i<p; i++) {
      Double_t xval, yval;
      band1->GetPoint(i,xval,yval);
      band->SetPoint(i,xval,yval);
      band2->GetPoint(i,xval,yval);
      band->SetPoint(2*p-i-1,xval,yval);
    }
    if (style==3) {
      band1->Draw();
      band2->Draw();
    }
    else
      band->Draw("f");
  }  
}

void drawSystErrors(TGraphAsymmErrors* g, Float_t err, 
		    Int_t style=0, Int_t color=16, Bool_t c=kFALSE) 
{
  // cap sizes
  Float_t dx = 0.03;
  Float_t dy = 0.006;
  
  TGraph* band1 = new TGraph();
  TGraph* band2 = new TGraph();
  Int_t p=0;
  
  for (Int_t b=0; b<g->GetN(); b++) {
    Double_t x = g->GetX()[b];
    Double_t y = g->GetY()[b];

    Double_t xh = x + g->GetEXhigh()[b];
    Double_t xl = x - g->GetEXlow()[b];
    Double_t yh = y + g->GetEYhigh()[b];
    Double_t yl = y - g->GetEYlow()[b];
    
    if (c) {
      yh = y+TMath::Sqrt((g->GetEYhigh()[b]*g->GetEYhigh()[b])+(y*err*y*err));
      yl = y-TMath::Sqrt((g->GetEYlow()[b]*g->GetEYlow()[b])  +(y*err*y*err));
    }
    
    // boxes
    if (style==0) {
      TBox* box = new TBox(xl,yl,xh,yh);
      box->SetFillColor(color);
      box->SetLineColor(color);
      box->SetFillStyle(1001);
      box->Draw();
    }
    // bands
    if (style==1||style==2) {
      band1->SetPoint(p,x,yl);
      band2->SetPoint(p,x,yh);
      p++;
    }
  }
  if (style==1||style==2) {
    
    band1->SetLineColor(color);
    band2->SetLineColor(color);
    band1->SetFillColor(color);
    band2->SetFillColor(color);
    
    TGraph* band= new TGraph(2*p);
    band->SetLineColor(color);
    band->SetFillColor(color);
    for (Int_t i=0; i<p; i++) {
      Double_t x = band1->GetX()[i];
      band->SetPoint(i,band1->GetX()[i],band1->GetY()[i]);
      band->SetPoint(2*p-i-1,band2->GetX()[i],band2->GetY()[i]);
    }
    if (style==1) {
      band1->Draw();
      band2->Draw();
    }
    else
      band->Draw("f");
  }
}