rf205_compplot.C

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/// \file
/// \ingroup tutorial_roofit
/// \notebook -js -nodraw
/// Addition and convolution: options for plotting components of composite p.d.f.s.
///
/// \macro_image
/// \macro_output
/// \macro_code
/// \author 07/2008 - Wouter Verkerke

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

void rf205_compplot()
{
   // S e t u p   c o m p o s i t e    p d f
   // --------------------------------------

   // 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 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);

   // 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);

   // 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("sig1frac", "fraction of component 1 in background", 0.2, 0., 1.);
   RooAddPdf bkg("bkg", "Signal", RooArgList(bkg1, bkg2), 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);

   // S e t u p   b a s i c   p l o t   w i t h   d a t a   a n d   f u l l   p d f
   // ------------------------------------------------------------------------------

   // Generate a data sample of 1000 events in x from model
   RooDataSet *data = model.generate(x, 1000);

   // Plot data and complete PDF overlaid
   RooPlot *xframe = x.frame(Title("Component plotting of pdf=(sig1+sig2)+(bkg1+bkg2)"));
   data->plotOn(xframe);
   model.plotOn(xframe);

   // Clone xframe for use below
   RooPlot *xframe2 = (RooPlot *)xframe->Clone("xframe2");

   // M a k e   c o m p o n e n t   b y   o b j e c t   r e f e r e n c e
   // --------------------------------------------------------------------

   // Plot single background component specified by object reference
   model.plotOn(xframe, Components(bkg), LineColor(kRed));

   // Plot single background component specified by object reference
   model.plotOn(xframe, Components(bkg2), LineStyle(kDashed), LineColor(kRed));

   // Plot multiple background components specified by object reference
   // Note that specified components may occur at any level in object tree
   // (e.g bkg is component of 'model' and 'sig2' is component 'sig')
   model.plotOn(xframe, Components(RooArgSet(bkg, sig2)), LineStyle(kDotted));

   // M a k e   c o m p o n e n t   b y   n a m e  /   r e g e x p
   // ------------------------------------------------------------

   // Plot single background component specified by name
   model.plotOn(xframe2, Components("bkg"), LineColor(kCyan));

   // Plot multiple background components specified by name
   model.plotOn(xframe2, Components("bkg1,sig2"), LineStyle(kDotted), LineColor(kCyan));

   // Plot multiple background components specified by regular expression on name
   model.plotOn(xframe2, Components("sig*"), LineStyle(kDashed), LineColor(kCyan));

   // Plot multiple background components specified by multiple regular expressions on name
   model.plotOn(xframe2, Components("bkg1,sig*"), LineStyle(kDashed), LineColor(kYellow), Invisible());

   // Draw the frame on the canvas
   TCanvas *c = new TCanvas("rf205_compplot", "rf205_compplot", 800, 400);
   c->Divide(2);
   c->cd(1);
   gPad->SetLeftMargin(0.15);
   xframe->GetYaxis()->SetTitleOffset(1.4);
   xframe->Draw();
   c->cd(2);
   gPad->SetLeftMargin(0.15);
   xframe2->GetYaxis()->SetTitleOffset(1.4);
   xframe2->Draw();
   c->Draw();
}