/*
this program compares the two branches of the two tree or the two branches from the same tree.
*/
void compareQuantities(string filename1, string filename2, string var1, string var2, string var3, int nbins, float min, float max, string cut=""){
//"abs(jgenEta[0])<5.0,jgenPt[0]>25" ){

	if (filename2 == "") filename2 = filename1;
	if (var2 == "") var2 = var1;

	gStyle->SetOptStat(0);
	gROOT->SetStyle("Plain");
//	gPad->SetLeftMargin(0.15);

	TFile *inputFile1 = new TFile(filename1.c_str());
	TFile *inputFile2 = new TFile(filename2.c_str());

	TTree *jetTree1 = (TTree *) inputFile1->Get("demo/tree");
	TTree *jetTree2 = (TTree *) inputFile2->Get("demo/tree");

	TH1F *var1H = new TH1F("var1H", "var1H", nbins, min, max);
	TH1F *var2H = new TH1F("var2H", "var2H", nbins, min, max);
	

//	cout << var1 << "  " << var2 << endl;	

	jetTree1->Draw(Form("%s>>var1H",var1.c_str()), cut.c_str(), "goff");
	jetTree2->Draw(Form("%s>>var2H",var2.c_str()), cut.c_str(), "goff");

	cout << var1H->GetEntries() << " " << var2H->GetEntries() << endl;

	var1H->SetLineWidth(2);
	var2H->SetLineWidth(2);

	var1H->SetLineColor(kRed);
	var2H->SetLineColor(kBlue);


	var1H->SetMaximum( TMath::Max(var1H->GetMaximum(), var2H->GetMaximum()) * 1.10 );

	var1H->GetXaxis()->SetTitle(TString(var3));
//	var1H->GetYaxis()->SetLabelOffset(0.5);
	var1H->GetYaxis()->SetTitle("Fraction of Events");
	var1H->GetYaxis()->SetTitleOffset(1.5);
//	var1H->GetYaxis()->SetNoExponent();

    if (var1==var2) 
    {
        var1H->GetXaxis()->SetTitle(var1.c_str());
        var1 = filename1;
        var2 = filename2;
    }
	var1H->Draw();
	gPad->Update();
//	TPaveStats *statsbox1 = (TPaveStats*)gPad->GetPrimitive("stats");
	TPaveStats *statsbox1 = (TPaveStats*)var1H->GetListOfFunctions()->FindObject("stats");
	statsbox1->SetX1NDC(0.50);    //set new y start position
	statsbox1->SetX2NDC(0.70);    //set new y end position
	statsbox1->SetY1NDC(0.90);    //set new y start position
	statsbox1->SetY2NDC(0.99);    //set new y end position
	statsbox1->SetTextColor(kRed);

	var2H->Draw("sames");
	gPad->Update();
//	TPaveStats *statsbox2 = (TPaveStats*)gPad->GetPrimitive("stats");
	TPaveStats *statsbox2 = (TPaveStats*)var2H->GetListOfFunctions()->FindObject("stats");
	statsbox2->SetX1NDC(0.70);    //set new y start position
	statsbox2->SetX2NDC(0.9);    //set new y end position
	statsbox2->SetY1NDC(0.90);    //set new y start position
	statsbox2->SetY2NDC(0.99);    //set new y end position
	statsbox2->SetTextColor(kBlue);

//	var1H->Draw();
//	var2H->Draw("sames");
	

	TLegend *leg = new TLegend(0.1,0.9,0.5,0.99);
	leg->SetFillColor(0);
	//leg->SetNColumns(2);
	leg->AddEntry(var1H, var1.c_str(), "l");
	leg->AddEntry(var2H, var2.c_str(), "l");
	leg->Draw("same");

}