Logo ROOT  
Reference Guide
BreitWigner.C
Go to the documentation of this file.
1/// \file
2/// \ingroup tutorial_math
3/// \notebook
4/// Tutorial illustrating how to create a plot comparing a Breit Wigner to a Relativistic Breit Wigner
5///
6/// can be run with:
7///
8/// ~~~{.cpp}
9/// root[0] .x BreitWigner.C
10/// ~~~
11///
12/// \macro_image
13/// \macro_code
14///
15/// \author Jack Lindon
16
17#include "TMath.h"
18
19#include <limits>
20#include <string>
21#include "TAxis.h"
22#include "TGraph.h"
23#include "TCanvas.h"
24#include "TLatex.h"
25#include "TLegend.h"
26#include "TStyle.h" //For gStyle to remove stat box.
27
28
29void plotTwoTGraphs(Double_t x[], Double_t y1[], Double_t y2[], const Int_t nPoints
30 , Double_t lowerXLimit, Double_t upperXLimit
31 , Double_t lowerYLimit, Double_t upperYLimit
32 , std::string legend1, std::string legend2
33 , std::string plotTitle1, std::string plotTitle2, std::string plotTitle3
34 , std::string pdfTitle){
35
36 ///////////////////////////////////////////////////////
37 //Define variables for plot aesthetics and positioning
38 Double_t legendXPos = 0.63; Double_t legendYPos = 0.85;
39 Double_t legendXWidth = 0.29; Double_t legendYHeight = 0.1;
40 Double_t plotTitleXPos = 0.23; Double_t plotTitleYPos = 0.25;
41 Double_t fontSize = 0.04;
42 Double_t lineWidth = 2;
43 bool setLimitPlotLogScale = true;
44 std::string xAxisTitle = "E [GeV]"; std::string yAxisTitle = "Events";
45 Double_t xAxisTitleOffset = 1; Double_t yAxisTitleOffset = 1.3;
47
48 ///////////////////////////////////////////////////////
49 // Initialize TGraphs
50 TGraph* gr1 = new TGraph(nPoints,x,y1);
51 TGraph* gr2 = new TGraph(nPoints,x,y2);
52 gr1->SetLineWidth(lineWidth);
53 gr2->SetLineWidth(lineWidth);
54 gr1->SetLineColor(kBlack);
55 gr2->SetLineColor(kBlue);
56
57 /////////////////////////////////////////////////////////
58 // Initialize canvas
59 TCanvas* c1 = new TCanvas("c1","transparent pad",200,10,600,600);
60 c1->SetLogy(setLimitPlotLogScale);
61 c1->SetTicks(1,1);
62 c1->SetRightMargin(0.02);
63 c1->SetTopMargin(0.02);
64
65
66 ///////////////////////////////////////////////////////
67 //Make just a basic invisible TGraph just for the axes
68 const Double_t axis_x[2] = {lowerXLimit,upperXLimit};
69 const Double_t axis_y[2] = {lowerYLimit,upperYLimit};
70 TGraph* grAxis = new TGraph(2, axis_x, axis_y);
71 grAxis->SetTitle("");
72 grAxis->GetYaxis()->SetTitle(yAxisTitle.c_str());
73 grAxis->GetXaxis()->SetTitle(xAxisTitle.c_str());
74 grAxis->GetXaxis()->SetRangeUser(lowerXLimit,upperXLimit);
75 grAxis->GetYaxis()->SetRangeUser(lowerYLimit,upperYLimit);
76 grAxis->GetXaxis()->SetLabelSize(fontSize);
77 grAxis->GetYaxis()->SetLabelSize(fontSize);
78 grAxis->GetXaxis()->SetTitleSize(fontSize);
79 grAxis->GetYaxis()->SetTitleSize(fontSize);
80 grAxis->GetXaxis()->SetTitleOffset(xAxisTitleOffset);
81 grAxis->GetYaxis()->SetTitleOffset(yAxisTitleOffset);
82 grAxis->SetLineWidth(0);//So invisible
83
84 ///////////////////////////////////////////////////////////
85 // Make legend and set aesthetics
86 auto legend = new TLegend(legendXPos,legendYPos,legendXPos+legendXWidth,legendYPos+legendYHeight);
87 legend->SetFillStyle(0);
88 legend->SetBorderSize(0);
89 legend->SetTextSize(fontSize);
90 legend->AddEntry(gr1,legend1.c_str(),"L");
91 legend->AddEntry(gr2,legend2.c_str(),"L");
92
93
94 /////////////////////////////////////////////////////////////
95 // Add plot title to plot. Make in three lines so not crowded.
96 // Shift each line down by shiftY
97 float shiftY{0.037};
98 TLatex* tex_Title = new TLatex(plotTitleXPos,plotTitleYPos-0*shiftY,plotTitle1.c_str());
99 tex_Title->SetNDC();
100 tex_Title->SetTextFont(42);
101 tex_Title->SetTextSize(fontSize);
102 tex_Title->SetLineWidth(lineWidth);
103 TLatex* tex_Title2 = new TLatex(plotTitleXPos,plotTitleYPos-1*shiftY,plotTitle2.c_str());
104 tex_Title2->SetNDC();
105 tex_Title2->SetTextFont(42);
106 tex_Title2->SetTextSize(fontSize);
107 tex_Title2->SetLineWidth(lineWidth);
108 TLatex* tex_Title3 = new TLatex(plotTitleXPos,plotTitleYPos-2*shiftY,plotTitle3.c_str());
109 tex_Title3->SetNDC();
110 tex_Title3->SetTextFont(42);
111 tex_Title3->SetTextSize(fontSize);
112 tex_Title3->SetLineWidth(lineWidth);
113
114
115 /////////////////////////////////////
116 // Draw everything
117 grAxis->Draw("AL");
118 gr1->Draw("L same");
119 gr2->Draw("L same");
120 legend->Draw();
121 tex_Title->Draw();
122 tex_Title2->Draw();
123 tex_Title3->Draw();
124 c1->RedrawAxis(); //Be sure to redraw axis AFTER plotting TGraphs otherwise TGraphs will be on top of tick marks and axis borders.
125
126 gPad->Print(pdfTitle.c_str());
127
128}
129
130
131void BreitWigner(){
132
133 /////////////////////////////////////////////////////////
134 // Define x axis limits and steps for each plotted point
135 const Int_t nPoints = 1000;
136 Double_t xMinimum = 0; Double_t xMaximum = 13000;
137 Double_t xStepSize = (xMaximum-xMinimum)/nPoints;
138
139 ///////////////////////////////////////////////////////
140 // Define arrays of (x,y) points.
141 Double_t x[nPoints];
142 Double_t y_nonRelBW[nPoints], y_relBW[nPoints];
143
144
145 //////////////////////////////////
146 // Define Breit-Wigner parameters
147 Double_t width = 1350;
148 Double_t sigma = 269.7899;
149 Double_t median = 9000;
150
151 ///////////////////////////////////////////////////
152 // Loop over x axis range, filling in (x,y) points,
153 // and finding y minimums and maximums for axis limit.
154 Double_t yMinimum = std::numeric_limits<Double_t>::max();
155 Double_t yMaximum = TMath::BreitWignerRelativistic(median,median,width); //y maximum is at x=median (and non relativistic = relativistic at median so choice of function does not matter).
156 for (Int_t i=0;i<nPoints;i++) {
157 Double_t currentX = xMinimum+i*xStepSize;
158 x[i] = currentX;
159 y_nonRelBW[i] = TMath::BreitWigner(currentX,median,width);
160 y_relBW[i] = TMath::BreitWignerRelativistic(currentX,median,width);
161
162 if (y_nonRelBW[i]<yMinimum){yMinimum = y_nonRelBW[i];}
163 if (y_relBW[i]<yMinimum){yMinimum = y_relBW[i];}
164 }
165
166 plotTwoTGraphs(x, y_nonRelBW, y_relBW, nPoints
167 , xMinimum, xMaximum //xAxis limits
168 , yMinimum/4, yMaximum*4 //yAxis limits, expand for aesthetics.
169 ,"NonRel BW", "Rel BW" //Legend entries
170 , "Comparing BW", "M = " + std::to_string(int(round(median))) + " GeV", "#Gamma = " + std::to_string(int(round(width))) + " GeV" //Plot Title entry (three lines)
171 , "BW_M"+std::to_string(int(round(median)))+"_Gamma" + std::to_string(int(round(width))) +".pdf)" //PDF file title.
172 );
173}
int Int_t
Definition: RtypesCore.h:45
double Double_t
Definition: RtypesCore.h:59
@ kBlack
Definition: Rtypes.h:65
@ kBlue
Definition: Rtypes.h:66
Option_t Option_t TPoint TPoint const char y2
Option_t Option_t width
Option_t Option_t TPoint TPoint const char y1
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 SetLabelSize(Float_t size=0.04)
Set size of axis labels.
Definition: TAttAxis.cxx:206
virtual void SetTitleSize(Float_t size=0.04)
Set size of axis title.
Definition: TAttAxis.cxx:312
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 SetTextFont(Font_t tfont=62)
Set the text font.
Definition: TAttText.h:46
virtual void SetTextSize(Float_t tsize=1)
Set the text size.
Definition: TAttText.h:47
virtual void SetRangeUser(Double_t ufirst, Double_t ulast)
Set the viewing range for the axis from ufirst to ulast (in user coordinates, that is,...
Definition: TAxis.cxx:978
The Canvas class.
Definition: TCanvas.h:23
A TGraph is an object made of two arrays X and Y with npoints each.
Definition: TGraph.h:41
void Draw(Option_t *chopt="") override
Draw this graph with its current attributes.
Definition: TGraph.cxx:808
TAxis * GetXaxis() const
Get x axis of the graph.
Definition: TGraph.cxx:1553
TAxis * GetYaxis() const
Get y axis of the graph.
Definition: TGraph.cxx:1563
void SetTitle(const char *title="") override
Change (i.e.
Definition: TGraph.cxx:2338
To draw Mathematical Formula.
Definition: TLatex.h:18
This class displays a legend box (TPaveText) containing several legend entries.
Definition: TLegend.h:23
virtual void SetTitle(const char *title="")
Set the title of the TNamed.
Definition: TNamed.cxx:164
virtual void Draw(Option_t *option="")
Default Draw method for all objects.
Definition: TObject.cxx:274
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
virtual void SetNDC(Bool_t isNDC=kTRUE)
Set NDC mode on if isNDC = kTRUE, off otherwise.
Definition: TText.cxx:813
RVec< PromoteType< T > > round(const RVec< T > &v)
Definition: RVec.hxx:1815
const Double_t sigma
return c1
Definition: legend1.C:41
Double_t x[n]
Definition: legend1.C:17
Double_t BreitWigner(Double_t x, Double_t mean=0, Double_t gamma=1)
Calculates a Breit Wigner function with mean and gamma.
Definition: TMath.cxx:442
Double_t BreitWignerRelativistic(Double_t x, Double_t median=0, Double_t gamma=1)
Calculates a Relativistic Breit Wigner function with median and gamma.
Definition: TMath.cxx:452