rf109_chi2residpull.C: 'BASIC FUNCTIONALITY' RooFit tutorial macro #109
//////////////////////////////////////////////////////////////////////////
//
// 'BASIC FUNCTIONALITY' RooFit tutorial macro #109
//
// Calculating chi^2 from histograms and curves in RooPlots,
// making histogram of residual and pull distributions
//
//
//
// 07/2008 - Wouter Verkerke
//
/////////////////////////////////////////////////////////////////////////
#ifndef __CINT__
#include "RooGlobalFunc.h"
#endif
#include "RooRealVar.h"
#include "RooDataSet.h"
#include "RooGaussian.h"
#include "TCanvas.h"
#include "RooPlot.h"
#include "RooHist.h"
using namespace RooFit ;
void rf109_chi2residpull()
{
// S e t u p m o d e l
// ---------------------
// Create observables
RooRealVar x("x","x",-10,10) ;
// Create Gaussian
RooRealVar sigma("sigma","sigma",3,0.1,10) ;
RooRealVar mean("mean","mean",0,-10,10) ;
RooGaussian gauss("gauss","gauss",x,RooConst(0),sigma) ;
// Generate a sample of 1000 events with sigma=3
RooDataSet* data = gauss.generate(x,10000) ;
// Change sigma to 3.15
sigma=3.15 ;
// P l o t d a t a a n d s l i g h t l y d i s t o r t e d m o d e l
// ---------------------------------------------------------------------------
// Overlay projection of gauss with sigma=3.15 on data with sigma=3.0
RooPlot* frame1 = x.frame(Title("Data with distorted Gaussian pdf"),Bins(40)) ;
data->plotOn(frame1,DataError(RooAbsData::SumW2)) ;
gauss.plotOn(frame1) ;
// C a l c u l a t e c h i ^ 2
// ------------------------------
// Show the chi^2 of the curve w.r.t. the histogram
// If multiple curves or datasets live in the frame you can specify
// the name of the relevant curve and/or dataset in chiSquare()
cout << "chi^2 = " << frame1->chiSquare() << endl ;
// S h o w r e s i d u a l a n d p u l l d i s t s
// -------------------------------------------------------
// Construct a histogram with the residuals of the data w.r.t. the curve
RooHist* hresid = frame1->residHist() ;
// Construct a histogram with the pulls of the data w.r.t the curve
RooHist* hpull = frame1->pullHist() ;
// Create a new frame to draw the residual distribution and add the distribution to the frame
RooPlot* frame2 = x.frame(Title("Residual Distribution")) ;
frame2->addPlotable(hresid,"P") ;
// Create a new frame to draw the pull distribution and add the distribution to the frame
RooPlot* frame3 = x.frame(Title("Pull Distribution")) ;
frame3->addPlotable(hpull,"P") ;
TCanvas* c = new TCanvas("rf109_chi2residpull","rf109_chi2residpull",900,300) ;
c->Divide(3) ;
c->cd(1) ; frame1->Draw() ;
c->cd(2) ; frame2->Draw() ;
c->cd(3) ; frame3->Draw() ;
}
Last change: Wed Dec 17 10:56:32 2008
Last generated: 2008-12-17 10:56
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