Guys…
Well, I would like to fit a histogram using two regions (sideband regions). I have looked on the web, the forums, and underneath my desk for information on how to do this using RooFit. I have put together the following code based on the information that I was able to put together.
#include <iostream>
#include <string>
#include <TFile.h>
#include <TH1D.h>
#include <RooGlobalFunc.h>
#include <RooPlot.h>
#include <RooDataHist.h>
#include <RooRealVar.h>
#include <TCanvas.h>
#include "roothreshold.h"
#include <RooFitResult.h>
#include <RooCategory.h>
using namespace std;
using namespace RooFit;
typedef struct {
double delta;
double exp;
double exp_err;
double pull;
int fit_status;
} Result;
Result doFit(TH1*);
int main() {
TFile input("output_histos.root");
TH1D *input_hist = (TH1D*) input.FindObjectAny("data_0tag_rev1_nocuts_jj");
// Ok, lets make a RooFit thingy here
Result tmpres = doFit(input_hist);
cout << "The exp is: " << tmpres.exp << endl;
}
Result doFit(TH1 *input_histo) {
Result res;
double signal_count = input_histo->Integral(input_histo->FindBin(50), input_histo->FindBin(100));
RooRealVar x("x", "M(jj)", 0, 400, "GeV/c^{2}");
RooRealVar norm("norm", "norm", 1.0, 0.0, 100.0);
RooRealVar offset("offset", "offset", 10.849, 0, 30);
RooRealVar power("power", "power", 2.4653, 0, 10);
RooRealVar coeff1("coeff1", "coeff1", -0.0829876, -2, 2);
RooRealVar coeff2("coeff2", "coeff2", 0.000133946, -1, 1);
RooThreshold thresh("thresh", "MN_FIT Threshold Function", x, norm, offset, power, coeff1, coeff2);
RooDataHist data("data", "Yhea", x, input_histo);
RooCategory modes("modes","modes");
modes.defineType("1", 1);
modes.defineType("2", 2);
// Set the regions
x.setRange("low", 0, 50);
x.setRange("signal", 50, 100);
x.setRange("high", 100, 300);
x.setRange("fit_1", 30, 50);
x.setRange("fit_2", 100, 200);
// Get the original integral
RooAbsReal *preInt = thresh.createIntegral(x);
RooAbsReal *preIntSignal = thresh.createIntegral(x, Range("signal"));
RooAbsReal *preIntSideband = thresh.createIntegral(x, Range("low"), Range("high"));
preInt->Print();
cout << "The int is: " << preInt->getVal() << endl;
cout << "The signal region is: " << preIntSignal->getVal() << endl;
cout << "The sideband region is: " << preIntSideband->getVal() << endl;
cout << "The sum of the two is: " << preIntSignal->getVal() + preIntSideband->getVal() << endl;
// Do the fit
RooFitResult *fitResult = thresh.fitTo(data, Range("fit"), SplitRange(kTRUE), Verbose(kTRUE), Save(kTRUE), PrintLevel(3));
int status = fitResult->status();
int covQual = fitResult->covQual();
cout << "The fit status was: " << status << " with a covariance quality code of: " << covQual << endl;
RooAbsReal *postInt = thresh.createIntegral(x);
RooAbsReal *postIntSignal = thresh.createIntegral(x, Range("signal"));
RooAbsReal *postIntSideband = thresh.createIntegral(x, Range("low"), Range("high"));
cout << "The post fit signal integral is: " << postIntSignal->getVal() << endl;
cout << "The number of signal events is : " << signal_count << endl;
TCanvas *can = new TCanvas("mycanvas");
RooPlot *frame = x.frame();
data.plotOn(frame);
thresh.plotOn(frame);
frame->SetTitle("M(jj) Fit with a Threshold Function");
frame->Draw();
can->SaveAs("test.eps");
}I have been looking in the output but I can not seem to find a way to verify that it is using just the fit_* regions. It looks like it is using the entire region. Thanks for any help here. I may have this right, if I do please let me know. I am using root version 5.18/00d.
Justace