void qqtest() {
	TCanvas *canvas = new TCanvas("canvas", "qqtest", 0, 0, 600, 800);
	canvas->Divide(1, 2);
	TFile *file = new TFile("qqdat.root");
	TTree *tree = (TTree*)file->Get("h3");
	canvas->cd(1);
	tree->Draw("Decg*TMath::RadToDeg()>>hist(40,30,70)", "1/cos(Decg)");
	TF1 *fcn = new TF1("fcn", &fcn_xpsr, -90, 90, 1);
	fcn->SetParameter(0, 800);
	hist->Fit(fcn);
	canvas->cd(2);
	TGraphQQ *graph = new TGraphQQ(tree->GetSelectedRows(), tree->GetV1(), fcn);
	graph->Draw("al");
}


Double_t fcn_xpsr(Double_t *x, Double_t *params) {
	static Double_t lat = TMath::DegToRad()*49.0994;
	static Double_t maxze = TMath::DegToRad()*18.0;
	Double_t dec = x[0]*TMath::DegToRad();
	Double_t xi = (cos(maxze)-sin(lat)*sin(dec))/(cos(lat)*cos(dec));
	Double_t alpha_m;
	if (xi > 1) alpha_m = 0;
	else if (xi < -1) alpha_m = TMath::Pi();
	else alpha_m = TMath::ACos(xi);
	return params[0]*(cos(lat)*cos(dec)*sin(alpha_m)+alpha_m*sin(lat)*sin(dec));
}