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Reference Guide
GammaFun.C File Reference

Detailed Description

View in nbviewer Open in SWAN 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("htmp","",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:414
#define gPad
Definition: TVirtualPad.h:288
virtual void SetTitleOffset(Float_t offset=1)
Set distance between the axis and the axis title.
Definition: TAttAxis.cxx:301
virtual void SetTitleSize(Float_t size=0.04)
Set size of axis title.
Definition: TAttAxis.cxx:312
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:213
TAxis * GetYaxis() const
Get y axis of the function.
Definition: TF1.cxx:2429
virtual void SetRange(Double_t xmin, Double_t xmax)
Initialize the upper and lower bounds to draw the function.
Definition: TF1.cxx:3570
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:3600
void Draw(Option_t *option="") override
Draw this function with its current attributes.
Definition: TF1.cxx:1347
virtual TF1 * DrawCopy(Option_t *option="") const
Draw a copy of this function with its current attributes.
Definition: TF1.cxx:1377
TAxis * GetXaxis() const
Get x axis of the function.
Definition: TF1.cxx:2418
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:260
1-D histogram with a float per channel (see TH1 documentation)}
Definition: TH1.h:574
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.
Definition: TPaveLabel.cxx:87
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:1589
return c1
Definition: legend1.C:41
Author
Magdalena Slawinska

Definition in file GammaFun.C.