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GammaFun.C File Reference

Detailed Description

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Example showing the usage of the major special math functions (gamma, beta, erf) in ROOT To execute the macro type in:

root[0]: .x GammaFun.C

It will create one canvas with the representation of the tgamma, lgamma, beta, erf and erfc functions

#include "TMath.h"
#include "TF1.h"
#include "TF2.h"
#include "TSystem.h"
#include "TCanvas.h"
#include "TStyle.h"
#include "TPaveLabel.h"
#include "TAxis.h"
#include "TH1.h"
void GammaFun() {
TF1 *f1a = new TF1("Gamma(x)","ROOT::Math::tgamma(x)",-2,5);
TF1 *f2a = new TF1("f2a","ROOT::Math::lgamma(x)",0,10);
TF2 *f3a = new TF2("Beta(x)","ROOT::Math::beta(x, y)",0,0.1, 0, 0.1);
TF1 *f4a = new TF1("erf(x)","ROOT::Math::erf(x)",0,5);
TF1 *f4b = new TF1("erfc(x)","ROOT::Math::erfc(x)",0,5);
TCanvas *c1 = new TCanvas("c1", "Gamma and related functions",800,700);
c1->Divide(2,2);
c1->cd(1);
gPad->SetGrid();
//setting the title in a label style
TPaveLabel *p1 = new TPaveLabel(.1,.90 , (.1+.50),(.90+.10) ,"ROOT::Math::tgamma(x)", "NDC");
p1->SetFillColor(0);
p1->SetTextFont(22);
//setting graph
// draw axis first (use TH1 to draw the frame)
TH1F * h = new TH1F("hTemp","",500,-2,5);
h->SetMinimum(-20);
h->SetMaximum(20);
h->GetXaxis()->SetTitleSize(0.06);
h->GetXaxis()->SetTitleOffset(.7);
h->GetXaxis()->SetTitle("x");
h->Draw();
// draw the functions 3 times in the separate ranges to avoid singularities
f1a->SetLineWidth(2);
f1a->SetRange(-2,-1);
f1a->DrawCopy("same");
f1a->SetRange(-1,0);
f1a->DrawCopy("same");
f1a->SetRange(0,5);
f1a->DrawCopy("same");
p1->Draw();
c1->cd(2);
gPad->SetGrid();
TPaveLabel *p2 = new TPaveLabel(.1,.90 , (.1+.50),(.90+.10) ,"ROOT::Math::lgamma(x)", "NDC");
p2->SetFillColor(0);
p2->SetTextFont(22);
f2a->SetLineWidth(2);
f2a->GetXaxis()->SetTitle("x");
f2a->GetXaxis()->SetTitleSize(0.06);
f2a->GetXaxis()->SetTitleOffset(.7);
f2a->SetTitle("");
f2a->Draw();
p2->Draw();
c1->cd(3);
gPad->SetGrid();
TPaveLabel *p3 = new TPaveLabel(.1,.90 , (.1+.50),(.90+.10) ,"ROOT::Math::beta(x, y)", "NDC");
p3->SetFillColor(0);
p3->SetTextFont(22);
f3a->SetLineWidth(2);
f3a->GetXaxis()->SetTitle("x");
f3a->GetXaxis()->SetTitleOffset(1.2);
f3a->GetXaxis()->SetTitleSize(0.06);
f3a->GetYaxis()->SetTitle("y");
f3a->GetYaxis()->SetTitleSize(0.06);
f3a->GetYaxis()->SetTitleOffset(1.5);
f3a->SetTitle("");
f3a->Draw("surf1");//option for a 3-dim plot
p3->Draw();
c1->cd(4);
gPad->SetGrid();
TPaveLabel *p4 = new TPaveLabel(.1,.90 , (.1+.50),(.90+.10) ,"erf(x) and erfc(x)", "NDC");
p4->SetFillColor(0);
p4->SetTextFont(22);
f4a->SetTitle("erf(x) and erfc(x)");
f4a->SetLineWidth(2);
f4b->SetLineWidth(2);
f4a->GetXaxis()->SetTitleSize(.06);
f4a->GetXaxis()->SetTitleOffset(.7);
f4a->GetXaxis()->SetTitle("x");
f4a->Draw();
f4b->Draw("same");//option for a multiple graph plot
f4a->SetTitle("");
p4->Draw();
}
#define h(i)
Definition RSha256.hxx:106
@ kRed
Definition Rtypes.h:66
@ kBlack
Definition Rtypes.h:65
@ kBlue
Definition Rtypes.h:66
R__EXTERN TStyle * gStyle
Definition TStyle.h:436
#define gPad
virtual void SetTitleOffset(Float_t offset=1)
Set distance between the axis and the axis title.
Definition TAttAxis.cxx:298
virtual void SetTitleSize(Float_t size=0.04)
Set size of axis title.
Definition TAttAxis.cxx:309
virtual void SetFillColor(Color_t fcolor)
Set the fill area color.
Definition TAttFill.h:37
virtual void SetLineWidth(Width_t lwidth)
Set the line width.
Definition TAttLine.h:43
virtual void SetLineColor(Color_t lcolor)
Set the line color.
Definition TAttLine.h:40
virtual void SetTextColor(Color_t tcolor=1)
Set the text color.
Definition TAttText.h:44
virtual void SetTextFont(Font_t tfont=62)
Set the text font.
Definition TAttText.h:46
The Canvas class.
Definition TCanvas.h:23
1-Dim function class
Definition TF1.h:233
TAxis * GetYaxis() const
Get y axis of the function.
Definition TF1.cxx:2411
virtual void SetRange(Double_t xmin, Double_t xmax)
Initialize the upper and lower bounds to draw the function.
Definition TF1.cxx:3528
void SetTitle(const char *title="") override
Set function title if title has the form "fffffff;xxxx;yyyy", it is assumed that the function title i...
Definition TF1.cxx:3558
void Draw(Option_t *option="") override
Draw this function with its current attributes.
Definition TF1.cxx:1335
virtual TF1 * DrawCopy(Option_t *option="") const
Draw a copy of this function with its current attributes.
Definition TF1.cxx:1365
TAxis * GetXaxis() const
Get x axis of the function.
Definition TF1.cxx:2400
A 2-Dim function with parameters.
Definition TF2.h:29
void Draw(Option_t *option="") override
Draw this function with its current attributes.
Definition TF2.cxx:259
1-D histogram with a float per channel (see TH1 documentation)
Definition TH1.h:622
virtual void SetTitle(const char *title="")
Set the title of the TNamed.
Definition TNamed.cxx:164
A Pave (see TPave) with a text centered in the Pave.
Definition TPaveLabel.h:20
void Draw(Option_t *option="") override
Draw this pavelabel with its current attributes.
void SetOptStat(Int_t stat=1)
The type of information printed in the histogram statistics box can be selected via the parameter mod...
Definition TStyle.cxx:1640
return c1
Definition legend1.C:41
Author
Magdalena Slawinska

Definition in file GammaFun.C.