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Reference Guide
exampleFunctor.C File Reference

Detailed Description

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Tutorial illustrating how creating a TF1 class using functor or class member functions

can be run with:

root > .x exampleFunctor.C
root > .x exampleFunctor.C+ with ACLIC
#include "TF1.h"
#include "TMath.h"
#include "TLegend.h"
double MyFunc (double *x, double *p ) {
return TMath::Gaus(x[0],p[0],p[1] );
}
// function object (functor)
struct MyDerivFunc {
MyDerivFunc(TF1 * f): fFunc(f) {}
double operator() (double *x, double * ) const {
return fFunc->Derivative(*x);
}
TF1 * fFunc;
};
// function class with a member function
struct MyIntegFunc {
MyIntegFunc(TF1 * f): fFunc(f) {}
double Integral (double *x, double * ) const {
double a = fFunc->GetXmin();
return fFunc->Integral(a, *x);
}
TF1 * fFunc;
};
void exampleFunctor() {
double xmin = -10; double xmax = 10;
// create TF1 using a free C function
TF1 * f1 = new TF1("f1",MyFunc,xmin,xmax,2);
f1->SetParameters(0.,1.);
f1->Draw();
// Derivative function
// example to create TF1 using a functor
// in order to work with interpreter the function object must be created and lived all time for all time
// of the TF1. In compiled mode, the function object can be passed by value (recommended) and there
// is also no need to specify the type of the function class. Example is as follows:
//
// `TF1 * f2 = new TF1("f2",MyDerivFunc(f1), xmin, xmax,0); // only for C++ compiled mode`
MyDerivFunc * deriv = new MyDerivFunc(f1);
TF1 * f2 = new TF1("f2",deriv, xmin, xmax, 0);
f2->Draw("same");
// integral function
// example to create a TF1 using a member function of a user class
// in order to work with interpreter the function object must be created and lived all time for all time
// of the TF1. In compiled mode there is no need to specify the type of the function class and the name
// of the member function
//
// `TF1 * f3 = new TF1("f3",intg,&MyIntegFunc::Integral,xmin,xmax, 0); // only for C++ compiled mode`
MyIntegFunc * intg = new MyIntegFunc(f1);
TF1 * f3 = new TF1("f3",intg,&MyIntegFunc::Integral, xmin, xmax, 0);
f3->Draw("same");
TLegend * l = new TLegend(0.78, 0.25, 0.97 ,0.45);
l->AddEntry(f1, "Func");
l->AddEntry(f2, "Deriv.");
l->AddEntry(f3, "Integral");
l->Draw();
}
#define f(i)
Definition: RSha256.hxx:104
@ kRed
Definition: Rtypes.h:66
@ kBlue
Definition: Rtypes.h:66
winID h TVirtualViewer3D TVirtualGLPainter p
float xmin
Definition: THbookFile.cxx:95
float xmax
Definition: THbookFile.cxx:95
TRObject operator()(const T1 &t1) const
virtual void SetLineColor(Color_t lcolor)
Set the line color.
Definition: TAttLine.h:40
1-Dim function class
Definition: TF1.h:213
virtual void SetMaximum(Double_t maximum=-1111)
Set the maximum value along Y for this function In case the function is already drawn,...
Definition: TF1.cxx:3429
void Draw(Option_t *option="") override
Draw this function with its current attributes.
Definition: TF1.cxx:1334
virtual void SetMinimum(Double_t minimum=-1111)
Set the minimum value along Y for this function In case the function is already drawn,...
Definition: TF1.cxx:3442
virtual void SetParameters(const Double_t *params)
Definition: TF1.h:649
This class displays a legend box (TPaveText) containing several legend entries.
Definition: TLegend.h:23
virtual void Draw(Option_t *option="")
Default Draw method for all objects.
Definition: TObject.cxx:274
Double_t x[n]
Definition: legend1.C:17
TF1 * f1
Definition: legend1.C:11
Double_t Gaus(Double_t x, Double_t mean=0, Double_t sigma=1, Bool_t norm=kFALSE)
Calculates a gaussian function with mean and sigma.
Definition: TMath.cxx:471
TLine l
Definition: textangle.C:4
TArc a
Definition: textangle.C:12
Author
Lorenzo Moneta

Definition in file exampleFunctor.C.