rf509_wsinteractive.C: 'ORGANIZATION AND SIMULTANEOUS FITS' RooFit tutorial macro #509

/////////////////////////////////////////////////////////////////////////
//
// 'ORGANIZATION AND SIMULTANEOUS FITS' RooFit tutorial macro #509
// 
//  Easy CINT interactive access to workspace contents through a 
//  'C++' namespace in CINT that maps the workspace contents in a typesafe way
//
//  *********************************************************************************
//  *** NB: This macro exploits a feature native to CINT and _cannot_ be compiled ***
//  *********************************************************************************
//
// 04/2009 - Wouter Verkerke 
//
/////////////////////////////////////////////////////////////////////////

#ifndef __CINT__
#include "RooGlobalFunc.h"
#endif
#include "RooRealVar.h"
#include "RooDataSet.h"
#include "RooGaussian.h"
#include "RooConstVar.h"
#include "RooChebychev.h"
#include "RooAddPdf.h"
#include "RooWorkspace.h"
#include "RooPlot.h"
#include "TCanvas.h"
#include "TAxis.h"
#include "TFile.h"
#include "TH1.h"
using namespace RooFit ;


void fillWorkspace(RooWorkspace& w) ;

void rf509_wsinteractive()
{
  // C r e a t e  a n d   f i l l   w o r k s p a c e
  // ------------------------------------------------

  // Create a workspace named 'w' that exports its contents to 
  // a same-name C++ namespace in CINT 'namespace w'.
  RooWorkspace* w = new RooWorkspace("w",kTRUE) ;

  // Fill workspace with p.d.f. and data in a separate function
  fillWorkspace(*w) ;

  // Print workspace contents
  w->Print() ;

  // U s e   w o r k s p a c e   c o n t e n t s   t h r o u g h   C I N T   C + +   n a m e s p a c e
  // -------------------------------------------------------------------------------------------------

  // Use the name space prefix operator to access the workspace contents
  RooDataSet* d = w::model.generate(w::x,1000) ;
  RooFitResult* r = w::model.fitTo(*d) ;

  RooPlot* frame = w::x.frame() ;
  d->plotOn(frame) ;


  // NB: The 'w::' prefix can be omitted if namespace w is imported in local namespace
  // in the usual C++ way
  using namespace w;
  model.plotOn(frame) ;
  model.plotOn(frame,Components(bkg),LineStyle(kDashed)) ;


  // Draw the frame on the canvas
  new TCanvas("rf509_wsinteractive","rf509_wsinteractive",600,600) ;
  gPad->SetLeftMargin(0.15) ; frame->GetYaxis()->SetTitleOffset(1.4) ; frame->Draw() ;


}




void fillWorkspace(RooWorkspace& w)
{
  // C r e a t e  p d f   a n d   f i l l   w o r k s p a c e
  // --------------------------------------------------------

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

  // Create two Gaussian PDFs g1(x,mean1,sigma) anf g2(x,mean2,sigma) and their paramaters
  RooRealVar mean("mean","mean of gaussians",5,0,10) ;
  RooRealVar sigma1("sigma1","width of gaussians",0.5) ;
  RooRealVar sigma2("sigma2","width of gaussians",1) ;

  RooGaussian sig1("sig1","Signal component 1",x,mean,sigma1) ;  
  RooGaussian sig2("sig2","Signal component 2",x,mean,sigma2) ;  
  
  // Build Chebychev polynomial p.d.f.  
  RooRealVar a0("a0","a0",0.5,0.,1.) ;
  RooRealVar a1("a1","a1",-0.2,0.,1.) ;
  RooChebychev bkg("bkg","Background",x,RooArgSet(a0,a1)) ;

  // Sum the signal components into a composite signal p.d.f.
  RooRealVar sig1frac("sig1frac","fraction of component 1 in signal",0.8,0.,1.) ;
  RooAddPdf sig("sig","Signal",RooArgList(sig1,sig2),sig1frac) ;

  // 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) ;

  w.import(model) ;

}