rf207_comptools.C

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/// \file
/// \ingroup tutorial_roofit
/// \notebook -nodraw
///  'ADDITION AND CONVOLUTION' RooFit tutorial macro #207
///
///  Tools and utilities for manipulation of composite objects
///
/// \macro_output
/// \macro_code
/// \author 07/2008 - Wouter Verkerke


#include "RooRealVar.h"
#include "RooDataSet.h"
#include "RooGaussian.h"
#include "RooChebychev.h"
#include "RooExponential.h"
#include "RooAddPdf.h"
#include "RooPlot.h"
#include "RooCustomizer.h"
#include "TCanvas.h"
#include "TAxis.h"
#include "TH1.h"
using namespace RooFit ;



void rf207_comptools()
{

   // S e t u p   c o m p o s i t e    p d f,   d a t a s e t
   // --------------------------------------------------------

   // Declare observable x
   RooRealVar x("x","x",0,10) ;

   // Create two Gaussian PDFs g1(x,mean1,sigma) anf g2(x,mean2,sigma) and their parameters
   RooRealVar mean("mean","mean of gaussians",5) ;
   RooRealVar sigma("sigma","width of gaussians",0.5) ;
   RooGaussian sig("sig","Signal component 1",x,mean,sigma) ;

   // Build Chebychev polynomial p.d.f.
   RooRealVar a0("a0","a0",0.5,0.,1.) ;
   RooRealVar a1("a1","a1",0.2,0.,1.) ;
   RooChebychev bkg1("bkg1","Background 1",x,RooArgSet(a0,a1)) ;

   // Build exponential pdf
   RooRealVar alpha("alpha","alpha",-1) ;
   RooExponential bkg2("bkg2","Background 2",x,alpha) ;

   // Sum the background components into a composite background p.d.f.
   RooRealVar bkg1frac("bkg1frac","fraction of component 1 in background",0.2,0.,1.) ;
   RooAddPdf bkg("bkg","Signal",RooArgList(bkg1,bkg2),bkg1frac) ;

   // Sum the composite signal and background
   RooRealVar bkgfrac("bkgfrac","fraction of background",0.5,0.,1.) ;
   RooAddPdf  model("model","g1+g2+a",RooArgList(bkg,sig),bkgfrac) ;



   // Create dummy dataset that has more observables than the above pdf
   RooRealVar y("y","y",-10,10) ;
   RooDataSet data("data","data",RooArgSet(x,y)) ;




   // ---------------------------------------------------
   // B a s i c   i n f o r m a t i o n   r e q u e s t s
   // ===================================================


   // G e t   l i s t   o f   o b s e r v a b l e s
   // ---------------------------------------------

   // Get list of observables of pdf in context of a dataset
   //
   // Observables are define each context as the variables
   // shared between a model and a dataset. In this case
   // that is the variable 'x'

   RooArgSet* model_obs = model.getObservables(data) ;
   model_obs->Print("v") ;


   // G e t   l i s t   o f   p a r a m e t e r s
   // -------------------------------------------

   // Get list of parameters, given list of observables
   RooArgSet* model_params = model.getParameters(x) ;
   model_params->Print("v") ;

   // Get list of parameters, given a dataset
   // (Gives identical results to operation above)
   RooArgSet* model_params2 = model.getParameters(data) ;
   model_params2->Print() ;


   // G e t   l i s t   o f   c o m p o n e n t s
   // -------------------------------------------

   // Get list of component objects, including top-level node
   RooArgSet* model_comps = model.getComponents() ;
   model_comps->Print("v") ;


   // -------------------------------------------------------------------------------
   // M o d i f i c a t i o n s   t o   s t r u c t u r e   o f   c o m p o s i t e s
   // ===============================================================================


   // Create a second Gaussian
   RooRealVar sigma2("sigma2","width of gaussians",1) ;
   RooGaussian sig2("sig2","Signal component 1",x,mean,sigma2) ;

   // Create a sum of the original Gaussian plus the new second Gaussian
   RooRealVar sig1frac("sig1frac","fraction of component 1 in signal",0.8,0.,1.) ;
   RooAddPdf sigsum("sigsum","sig+sig2",RooArgList(sig,sig2),sig1frac) ;

   // Construct a customizer utility to customize model
   RooCustomizer cust(model,"cust") ;

   // Instruct the customizer to replace node 'sig' with node 'sigsum'
   cust.replaceArg(sig,sigsum) ;

   // Build a clone of the input pdf according to the above customization
   // instructions. Each node that requires modified is clone so that the
   // original pdf remained untouched. The name of each cloned node is that
   // of the original node suffixed by the name of the customizer object
   //
   // The returned head node own all nodes that were cloned as part of
   // the build process so when cust_clone is deleted so will all other
   // nodes that were created in the process.
   RooAbsPdf* cust_clone = (RooAbsPdf*) cust.build(kTRUE) ;

   // Print structure of clone of model with sig->sigsum replacement.
   cust_clone->Print("t") ;


   delete cust_clone ;

}