float inputFormular(float x0) {
	float p0 = 0;
	float p1 = 1;
	float p2 = 2;

	return p0 +x0*p1 + x0*x0*p2;
}

Double_t GetValue(TLinearFitter *myFit, Double_t par0) {
		TVectorD params;
		myFit->GetParameters(params);
		float fitResult = params(0) 
						+ params(1)*par0 
						+ params(2)*par0*par0;
		return fitResult;
	}
	
	Double_t GetError(TLinearFitter *myFit, Double_t par0) {
		TVectorD errors;
		myFit->GetErrors(errors);
		TVectorD params;
		myFit->GetParameters(params);
		float fitResult = sqrt( 
						std::pow(errors(0),2) 
						+ std::pow((errors(1)*par0),2) 
						+ std::pow((errors(2)*par0*par0),2)
						);
		return fitResult;
		
	}
	
	TGraph * GetGraph1D(TLinearFitter *myFit, Double_t min, Double_t max, std::string opt) {
		TGraph *gr = new TGraph();
		Double_t stepwidth = (max-min)/10.;
		Double_t pVar;
		
		for (int i = 0; i < 10; i++) {
			
			pVar = min + stepwidth*i;
						
			if (opt == "ul") {
				gr->SetPoint(i,pVar, GetValue(myFit,pVar) + GetError(myFit,pVar));
			} else if (opt == "ll") {
				gr->SetPoint(i,pVar, GetValue(myFit,pVar) - GetError(myFit,pVar));
			} else if (opt == "mid") {
				gr->SetPoint(i,pVar, GetValue(myFit,pVar));
			}				
		}
		return gr;
		
	}

int LFtest2() {
		TLinearFitter *myFit = new TLinearFitter(1);
		myFit->SetFormula("1 ++ x[0] ++ x[0]*x[0]");
		
		Double_t params[1];
		Double_t val;
		
		auto rng = new TRandom();
		float sigma = 1000;
		
		TGraph *grSimple = new TGraph();
		
		
		for (int i = 0; i < 100; i++) {
			
			params[0] = 10; val = inputFormular(params[0]); val += rng->Gaus(0,sigma);
			myFit->AddPoint(params, val);
			grSimple->SetPoint(grSimple->GetN(), 10,val);
			params[0] = 20; val = inputFormular(params[0]); val += rng->Gaus(0,sigma);
			myFit->AddPoint(params, val);
			grSimple->SetPoint(grSimple->GetN(), 20,val);
			params[0] = 30; val = inputFormular(params[0]); val += rng->Gaus(0,sigma);
			myFit->AddPoint(params, val);
			grSimple->SetPoint(grSimple->GetN(), 30,val);
			
		}

	std::cout << "Evaluate..." << std::endl;
	myFit->Eval();
	
	TVectorD result;
	TVectorD error;
	
	myFit->GetParameters(result);
	myFit->GetErrors(error);
	
	for (int i = 0; i < 3; i++) {
		std::cout << "par[" << i << "]: " << result(i) << " +- " << error(i) << " TValue: " << myFit->GetParTValue(i) << " Significance: " << myFit->GetParSignificance(i) << std::endl;
	}
	std::cout << "Chisquare: " << myFit->GetChisquare() << std::endl;
	
	
	std::cout << "Calculating Point at (10,10,1):" << GetValue(myFit,10) << " +- " << GetError(myFit, 10) << std::endl;
	
	myFit->PrintResults(3);
	grSimple->Draw("a*");
	
	TGraph *grSimpleFromFitMID = GetGraph1D(myFit,10,30,"mid");
	TGraph *grSimpleFromFitUL = GetGraph1D(myFit,10,30,"ul");
	TGraph *grSimpleFromFitLL = GetGraph1D(myFit,10,30,"ll");
	
	grSimpleFromFitMID->Draw("l");
	grSimpleFromFitUL->Draw("l");
	grSimpleFromFitLL->Draw("l");
	



return 0;
}