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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:412
#define gPad
virtual void SetTitleOffset(Float_t offset=1)
Set distance between the axis and the axis title.
Definition TAttAxis.cxx:293
virtual void SetTitleSize(Float_t size=0.04)
Set size of axis title.
Definition TAttAxis.cxx:303
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:43
virtual void SetTextFont(Font_t tfont=62)
Set the text font.
Definition TAttText.h:45
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:2399
virtual void SetTitle(const char *title="")
Set function title if title has the form "fffffff;xxxx;yyyy", it is assumed that the function title i...
Definition TF1.cxx:3562
virtual void SetRange(Double_t xmin, Double_t xmax)
Initialize the upper and lower bounds to draw the function.
Definition TF1.cxx:3532
virtual void Draw(Option_t *option="")
Draw this function with its current attributes.
Definition TF1.cxx:1322
virtual TF1 * DrawCopy(Option_t *option="") const
Draw a copy of this function with its current attributes.
Definition TF1.cxx:1352
TAxis * GetXaxis() const
Get x axis of the function.
Definition TF1.cxx:2388
A 2-Dim function with parameters.
Definition TF2.h:29
virtual void Draw(Option_t *option="")
Draw this function with its current attributes.
Definition TF2.cxx:241
1-D histogram with a float per channel (see TH1 documentation)}
Definition TH1.h:575
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
virtual void Draw(Option_t *option="")
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:1589
return c1
Definition legend1.C:41
Author
Magdalena Slawinska

Definition in file GammaFun.C.