Logo ROOT   6.08/07
Reference Guide
rf301_composition.C File Reference

Detailed Description

View in nbviewer Open in SWAN 'MULTIDIMENSIONAL MODELS' RooFit tutorial macro #301

Multi-dimensional p.d.f.s through composition, e.g. substituting a p.d.f parameter with a function that depends on other observables

pdf = gauss(x,f(y),s) with f(y) = a0 + a1*y



Processing /mnt/build/workspace/root-makedoc-v608/rootspi/rdoc/src/v6-08-00-patches/tutorials/roofit/rf301_composition.C...
#include "RooRealVar.h"
#include "RooDataSet.h"
#include "RooGaussian.h"
#include "RooPolyVar.h"
#include "RooPlot.h"
#include "TCanvas.h"
#include "TAxis.h"
#include "TH1.h"
using namespace RooFit ;
void rf301_composition()
{
// S e t u p c o m p o s e d m o d e l g a u s s ( x , m ( y ) , s )
// -----------------------------------------------------------------------
// Create observables
RooRealVar x("x","x",-5,5) ;
RooRealVar y("y","y",-5,5) ;
// Create function f(y) = a0 + a1*y
RooRealVar a0("a0","a0",-0.5,-5,5) ;
RooRealVar a1("a1","a1",-0.5,-1,1) ;
RooPolyVar fy("fy","fy",y,RooArgSet(a0,a1)) ;
// Create gauss(x,f(y),s)
RooRealVar sigma("sigma","width of gaussian",0.5) ;
RooGaussian model("model","Gaussian with shifting mean",x,fy,sigma) ;
// S a m p l e d a t a , p l o t d a t a a n d p d f o n x a n d y
// ---------------------------------------------------------------------------------
// Generate 10000 events in x and y from model
RooDataSet *data = model.generate(RooArgSet(x,y),10000) ;
// Plot x distribution of data and projection of model on x = Int(dy) model(x,y)
RooPlot* xframe = x.frame() ;
data->plotOn(xframe) ;
model.plotOn(xframe) ;
// Plot x distribution of data and projection of model on y = Int(dx) model(x,y)
RooPlot* yframe = y.frame() ;
data->plotOn(yframe) ;
model.plotOn(yframe) ;
// Make two-dimensional plot in x vs y
TH1* hh_model = model.createHistogram("hh_model",x,Binning(50),YVar(y,Binning(50))) ;
hh_model->SetLineColor(kBlue) ;
// Make canvas and draw RooPlots
TCanvas *c = new TCanvas("rf301_composition","rf301_composition",1200, 400);
c->Divide(3);
c->cd(1) ; gPad->SetLeftMargin(0.15) ; xframe->GetYaxis()->SetTitleOffset(1.4) ; xframe->Draw() ;
c->cd(2) ; gPad->SetLeftMargin(0.15) ; yframe->GetYaxis()->SetTitleOffset(1.4) ; yframe->Draw() ;
c->cd(3) ; gPad->SetLeftMargin(0.20) ; hh_model->GetZaxis()->SetTitleOffset(2.5) ; hh_model->Draw("surf") ;
}
Author
07/2008 - Wouter Verkerke

Definition in file rf301_composition.C.