rf313_paramranges.C

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/// \file
/// \ingroup tutorial_roofit
/// \notebook -js
/// Multidimensional models: working with parametrized ranges to define non-rectangular regions for fitting and
/// integration
///
/// \macro_image
/// \macro_output
/// \macro_code
/// \author 07/2008 - Wouter Verkerke

#include "RooRealVar.h"
#include "RooDataSet.h"
#include "RooGaussian.h"
#include "RooConstVar.h"
#include "RooPolynomial.h"
#include "RooProdPdf.h"
#include "TCanvas.h"
#include "TAxis.h"
#include "RooPlot.h"
using namespace RooFit;

void rf313_paramranges()
{

   // C r e a t e   3 D   p d f
   // -------------------------

   // Define observable (x,y,z)
   RooRealVar x("x", "x", 0, 10);
   RooRealVar y("y", "y", 0, 10);
   RooRealVar z("z", "z", 0, 10);

   // Define 3 dimensional pdf
   RooRealVar z0("z0", "z0", -0.1, 1);
   RooPolynomial px("px", "px", x, RooConst(0));
   RooPolynomial py("py", "py", y, RooConst(0));
   RooPolynomial pz("pz", "pz", z, z0);
   RooProdPdf pxyz("pxyz", "pxyz", RooArgSet(px, py, pz));

   // D e f i n e d   n o n - r e c t a n g u l a r   r e g i o n   R   i n   ( x , y , z )
   // -------------------------------------------------------------------------------------

   //
   // R = Z[0 - 0.1*Y^2] * Y[0.1*X - 0.9*X] * X[0 - 10]
   //

   // Construct range parametrized in "R" in y [ 0.1*x, 0.9*x ]
   RooFormulaVar ylo("ylo", "0.1*x", x);
   RooFormulaVar yhi("yhi", "0.9*x", x);
   y.setRange("R", ylo, yhi);

   // Construct parametrized ranged "R" in z [ 0, 0.1*y^2 ]
   RooFormulaVar zlo("zlo", "0.0*y", y);
   RooFormulaVar zhi("zhi", "0.1*y*y", y);
   z.setRange("R", zlo, zhi);

   // C a l c u l a t e   i n t e g r a l   o f   n o r m a l i z e d   p d f   i n   R
   // ----------------------------------------------------------------------------------

   // Create integral over normalized pdf model over x,y,z in "R" region
   RooAbsReal *intPdf = pxyz.createIntegral(RooArgSet(x, y, z), RooArgSet(x, y, z), "R");

   // Plot value of integral as function of pdf parameter z0
   RooPlot *frame = z0.frame(Title("Integral of pxyz over x,y,z in region R"));
   intPdf->plotOn(frame);

   new TCanvas("rf313_paramranges", "rf313_paramranges", 600, 600);
   gPad->SetLeftMargin(0.15);
   frame->GetYaxis()->SetTitleOffset(1.6);
   frame->Draw();

   return;
}