doc/v606/rf111__derivatives_8C.html

#ifndef __CINT__

#include "RooGlobalFunc.h"

#endif

#include "RooRealVar.h"

#include "RooDataSet.h"

#include "RooGaussian.h"

#include "TCanvas.h"

#include "TAxis.h"

#include "RooPlot.h"

using namespace RooFit ;


void rf111_derivatives()

{

  // S e t u p   m o d e l

  // ---------------------


  // Declare variables x,mean,sigma with associated name, title, initial value and allowed range

  RooRealVar x("x","x",-10,10) ;

  RooRealVar mean("mean","mean of gaussian",1,-10,10) ;

  RooRealVar sigma("sigma","width of gaussian",1,0.1,10) ;


  // Build gaussian p.d.f in terms of x,mean and sigma

  RooGaussian gauss("gauss","gaussian PDF",x,mean,sigma) ;


  // C r e a t e   a n d   p l o t  d e r i v a t i v e s   w . r . t .   x

  // ----------------------------------------------------------------------


  // Derivative of normalized gauss(x) w.r.t. observable x

  RooAbsReal* dgdx = gauss.derivative(x,1) ;


  // Second and third derivative of normalized gauss(x) w.r.t. observable x

  RooAbsReal* d2gdx2 = gauss.derivative(x,2) ;

  RooAbsReal* d3gdx3 = gauss.derivative(x,3) ;


  // Construct plot frame in 'x'

  RooPlot* xframe = x.frame(Title("d(Gauss)/dx")) ;


  // Plot gauss in frame (i.e. in x)

  gauss.plotOn(xframe) ;


  // Plot derivatives in same frame

  dgdx->plotOn(xframe,LineColor(kMagenta)) ;

  d2gdx2->plotOn(xframe,LineColor(kRed)) ;

  d3gdx3->plotOn(xframe,LineColor(kOrange)) ;


  // C r e a t e   a n d   p l o t  d e r i v a t i v e s   w . r . t .   s i g m a

  // ------------------------------------------------------------------------------


  // Derivative of normalized gauss(x) w.r.t. parameter sigma

  RooAbsReal* dgds = gauss.derivative(sigma,1) ;


  // Second and third derivative of normalized gauss(x) w.r.t. parameter sigma

  RooAbsReal* d2gds2 = gauss.derivative(sigma,2) ;

  RooAbsReal* d3gds3 = gauss.derivative(sigma,3) ;


  // Construct plot frame in 'sigma'

  RooPlot* sframe = sigma.frame(Title("d(Gauss)/d(sigma)"),Range(0.,2.)) ;


  // Plot gauss in frame (i.e. in x)

  gauss.plotOn(sframe) ;


  // Plot derivatives in same frame

  dgds->plotOn(sframe,LineColor(kMagenta)) ;

  d2gds2->plotOn(sframe,LineColor(kRed)) ;

  d3gds3->plotOn(sframe,LineColor(kOrange)) ;


  // Draw all frames on a canvas

  TCanvas* c = new TCanvas("rf111_derivatives","rf111_derivatives",800,400) ;

  c->Divide(2) ;

  c->cd(1) ; gPad->SetLeftMargin(0.15) ; xframe->GetYaxis()->SetTitleOffset(1.6) ; xframe->Draw() ;

  c->cd(2) ; gPad->SetLeftMargin(0.15) ; sframe->GetYaxis()->SetTitleOffset(1.6) ; sframe->Draw() ;


}