rf104_classfactory.C

Go to the documentation of this file.

/// \file
/// \ingroup tutorial_roofit
/// \notebook -js
/// Basic functionality: The class factory for functions and p.d.f.s
///
///
///  NOTE: This demo uses code that is generated by the macro,
///        therefore it cannot be compiled in one step by ACliC.
///        To run this macro compiled with ACliC do
///
/// ~~~ {.cpp}
///          root>.x rf104_classfactory.C // run interpreted to generate code
///          root>.L MyPdfV3.cxx+         // Compile and load created class
///          root>.x rf104_classfactory.C+ // run compiled code
/// ~~~
///
/// \macro_image
/// \macro_output
/// \macro_code
/// \author 07/2008 - Wouter Verkerke

#include "RooRealVar.h"
#include "RooDataSet.h"
#include "RooGaussian.h"
#include "TCanvas.h"
#include "TAxis.h"
#include "RooPlot.h"
#include "RooClassFactory.h"
#include "TROOT.h"

using namespace RooFit;

void rf104_classfactory()
{
   // W r i t e   c l a s s   s k e l e t o n   c o d e
   // --------------------------------------------------

   // Write skeleton p.d.f class with variable x,a,b
   // To use this class,
   //    - Edit the file MyPdfV1.cxx and implement the evaluate() method in terms of x,a and b
   //    - Compile and link class with '.x MyPdfV1.cxx+'
   //
   RooClassFactory::makePdf("MyPdfV1", "x,A,B");

   // W i t h   a d d e d   i n i t i a l   v a l u e   e x p r e s s i o n
   // ---------------------------------------------------------------------

   // Write skeleton p.d.f class with variable x,a,b and given formula expression
   // To use this class,
   //    - Compile and link class with '.x MyPdfV2.cxx+'
   //
   RooClassFactory::makePdf("MyPdfV2", "x,A,B", "", "A*fabs(x)+pow(x-B,2)");

   // W i t h   a d d e d   a n a l y t i c a l   i n t e g r a l   e x p r e s s i o n
   // ---------------------------------------------------------------------------------

   // Write skeleton p.d.f class with variable x,a,b, given formula expression _and_
   // given expression for analytical integral over x
   // To use this class,
   //    - Compile and link class with '.x MyPdfV3.cxx+'
   //
   RooClassFactory::makePdf("MyPdfV3", "x,A,B", "", "A*fabs(x)+pow(x-B,2)", kTRUE, kFALSE,
                            "x:(A/2)*(pow(x.max(rangeName),2)+pow(x.min(rangeName),2))+(1./"
                            "3)*(pow(x.max(rangeName)-B,3)-pow(x.min(rangeName)-B,3))");

   // U s e   i n s t a n c e   o f   c r e a t e d   c l a s s
   // ---------------------------------------------------------

   // Compile MyPdfV3 class
   gROOT->ProcessLineSync(".x MyPdfV3.cxx+");

   // Create instance of MyPdfV3 class
   RooRealVar a("a", "a", 1);
   RooRealVar b("b", "b", 2, -10, 10);
   RooRealVar y("y", "y", -10, 10);

   // We need to hide the type to run in a ROOT macro
   RooWorkspace w("w");
   w.factory("MyPdfV3::pdf(y[-10,10], a[1], b[2,-10,10])");
   auto pdf = w.pdf("pdf");

   // Generate toy data from pdf and plot data and p.d.f on frame
   RooPlot *frame1 = y.frame(Title("Compiled class MyPdfV3"));
   RooDataSet *data = pdf->generate(y, 1000);
   pdf->fitTo(*data);
   data->plotOn(frame1);
   pdf->plotOn(frame1);

   // -----------------------------------------------------------------
   // C o m p i l e d   v e r s i o n   o f   e x a m p l e   r f 1 0 3
   // =================================================================

   // Declare observable x
   RooRealVar x("x", "x", -20, 20);

   // The RooClassFactory::makePdfInstance() function performs code writing, compiling, linking
   // and object instantiation in one go and can serve as a straight replacement of RooGenericPdf

   RooRealVar alpha("alpha", "alpha", 5, 0.1, 10);
   RooAbsPdf *genpdf =
      RooClassFactory::makePdfInstance("GenPdf", "(1+0.1*fabs(x)+sin(sqrt(fabs(x*alpha+0.1))))", RooArgSet(x, alpha));

   // Generate a toy dataset from the interpreted p.d.f
   RooDataSet *data2 = genpdf->generate(x, 50000);

   // Fit the interpreted p.d.f to the generated data
   genpdf->fitTo(*data2);

   // Make a plot of the data and the p.d.f overlaid
   RooPlot *frame2 = x.frame(Title("Compiled version of pdf of rf103"));
   data2->plotOn(frame2);
   genpdf->plotOn(frame2);

   // Draw all frames on a canvas
   TCanvas *c = new TCanvas("rf104_classfactory", "rf104_classfactory", 800, 400);
   c->Divide(2);
   c->cd(1);
   gPad->SetLeftMargin(0.15);
   frame1->GetYaxis()->SetTitleOffset(1.4);
   frame1->Draw();
   c->cd(2);
   gPad->SetLeftMargin(0.15);
   frame2->GetYaxis()->SetTitleOffset(1.4);
   frame2->Draw();
}