void Eres_vs_p_vs_theta(const char *suffix="")
{
	gROOT->Reset();
	gStyle->SetPalette(1);
	gStyle->SetPadRightMargin(0.15);
	
	TCanvas *c1 = new TCanvas("c1");
	c1->SetTicks();
	
	TFile *f = new TFile("hd_res_photon.root");
	TH2D *h = (TH2D*)gROOT->FindObject("dE_over_E_vs_p_vs_theta");
	h->SetTitle("Reconstructed #gamma energy resolution (relative) vs. p_{tot} and #theta");
	h->GetXaxis()->SetRangeUser(0.0, 130.0);
	h->SetZTitle("#sigma(#deltaE/E)");
	h->Draw("colz");
	
	AddStandardLabels(h);
	
	char fname[256];
	sprintf(fname, "Eres_vs_p_vs_theta%s.gif", suffix);
	c1->SaveAs(fname);
	sprintf(fname, "Eres_vs_p_vs_theta%s.pdf", suffix);
	c1->SaveAs(fname);
}

//----------------
// AddStandardLabels
//----------------
void AddStandardLabels(TH2D *axes=NULL)
{
	// This will draw a label or two on the
	// current plot using the NDC coordinates.
	// It is put here to make sure all plots have
	// a consistent labeling.
	
	// Date, Author
	TLatex *lab = new TLatex(0.4, 0.7, "Feb. 15, 2009 DL");
	ConvertFromNDC(lab, axes);
	lab->SetTextSize(0.03);
	lab->SetTextAlign(33);
	lab->Draw();

	// SVN Revision
	lab = new TLatex(0.4, 0.645, "svn revision: 4865");
	ConvertFromNDC(lab, axes);
	lab->SetTextSize(0.02);
	lab->SetTextAlign(31);
	lab->Draw();
	
	// Event type
	lab = new TLatex(0.275, 0.6, "Single #gamma");
	ConvertFromNDC(lab, axes);
	lab->SetTextSize(0.03);
	lab->SetTextAlign(31);
	lab->Draw();

}

//----------------
// ConvertFromNDC
//----------------
void ConvertFromNDC(TLatex *obj, TH2D *h=NULL)
{
	// Bugs in ROOT make it hard to plot labels consistently.
	// For 1D plots, the histogram axes define the coordinate
	// system. For 2D plots, we seem to be forced to use the
	// NDC. There does not seem to be an obvious way to tell
	// which we're using so we pass the information in in the
	// form of the "axes" histogram. If it is not NULL, then
	// we use it to define the limits. Otherwise, we do nothing.

	if(h==NULL)return;

	TAxis *xaxis = h->GetXaxis();
	int Nbinsx = xaxis->GetNbins();
	double xmin = xaxis->GetBinLowEdge(1);
	double xmax = xmin + xaxis->GetBinLowEdge(Nbinsx);

	TAxis *yaxis = h->GetYaxis();
	int Nbinsy = yaxis->GetNbins();
	double ymin = yaxis->GetBinLowEdge(1);
	double ymax = ymin + yaxis->GetBinLowEdge(Nbinsy);
	
	
	double x = obj->GetX();
	double y = obj->GetY();
	cout<<" in:  x="<<x<<"  y="<<y<<endl;
	
	x = xmin + (xmax-xmin)*(0.5+x/1.15);
	y = ymin + (ymax-ymin)*(0.5+y/1.15);
	
	obj->SetX(x);
	obj->SetY(y);

	cout<<"out:  x="<<x<<"  y="<<y<<endl;
}