ROOT   Reference Guide
graph2derrorsfit.C
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1/// \file
2/// \ingroup tutorial_graphs
3/// \notebook
4/// Draw and fit a TGraph2DErrors
5///
6/// \macro_image
7/// \macro_code
8///
9/// \author Olivier Couet
10
11#include <TMath.h>
12#include <TGraph2DErrors.h>
13#include <TRandom.h>
14#include <TStyle.h>
15#include <TCanvas.h>
16#include <TF2.h>
17
18void graph2derrorsfit()
19{
20 TCanvas *c1 = new TCanvas("c1");
21
22 Double_t rnd, x, y, z, ex, ey, ez;
23 Double_t e = 0.3;
24 Int_t nd = 500;
25
26 TRandom r;
27 TF2 *f2 = new TF2("f2","1000*(([0]*sin(x)/x)*([1]*sin(y)/y))+200",-6,6,-6,6);
28 f2->SetParameters(1,1);
29 TGraph2DErrors *dte = new TGraph2DErrors(nd);
30
31 // Fill the 2D graph
32 Double_t zmax = 0;
33 for (Int_t i=0; i<nd; i++) {
34 f2->GetRandom2(x,y);
35 rnd = r.Uniform(-e,e); // Generate a random number in [-e,e]
36 z = f2->Eval(x,y)*(1+rnd);
37 if (z>zmax) zmax = z;
38 dte->SetPoint(i,x,y,z);
39 ex = 0.05*r.Rndm();
40 ey = 0.05*r.Rndm();
41 ez = TMath::Abs(z*rnd);
42 dte->SetPointError(i,ex,ey,ez);
43 }
44
45 f2->SetParameters(0.5,1.5);
46 dte->Fit(f2);
47 TF2 *fit2 = (TF2*)dte->FindObject("f2");
48 fit2->SetTitle("Minuit fit result on the Graph2DErrors points");
49 fit2->SetMaximum(zmax);
51 fit2->SetLineColor(1);
52 fit2->SetLineWidth(1);
53 fit2->Draw("surf1");
54 dte->Draw("same p0");
55}
#define e(i)
Definition: RSha256.hxx:103
int Int_t
Definition: RtypesCore.h:45
double Double_t
Definition: RtypesCore.h:59
Option_t Option_t TPoint TPoint const char GetTextMagnitude GetFillStyle GetLineColor GetLineWidth GetMarkerStyle GetTextAlign GetTextColor GetTextSize void char Point_t Rectangle_t WindowAttributes_t Float_t r
R__EXTERN TStyle * gStyle
Definition: TStyle.h:414
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
The Canvas class.
Definition: TCanvas.h:23
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:3438
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:3596
virtual void SetParameters(const Double_t *params)
Definition: TF1.h:649
virtual Double_t Eval(Double_t x, Double_t y=0, Double_t z=0, Double_t t=0) const
Evaluate this function.
Definition: TF1.cxx:1455
A 2-Dim function with parameters.
Definition: TF2.h:29
virtual void GetRandom2(Double_t &xrandom, Double_t &yrandom, TRandom *rng=nullptr)
Return 2 random numbers following this function shape.
Definition: TF2.cxx:547
void Draw(Option_t *option="") override
Draw this function with its current attributes.
Definition: TF2.cxx:259
Graph 2D class with errors.
void SetPoint(Int_t i, Double_t x, Double_t y, Double_t z) override
Set x, y and z values for point number i.
virtual void SetPointError(Int_t i, Double_t ex, Double_t ey, Double_t ez)
Set ex, ey and ez values for point number i.
TObject * FindObject(const char *name) const override
search object named name in the list of functions
Definition: TGraph2D.cxx:769
virtual TFitResultPtr Fit(const char *formula, Option_t *option="", Option_t *goption="")
Fits this graph with function with name fname Predefined functions such as gaus, expo and poln are au...
Definition: TGraph2D.cxx:793
void Draw(Option_t *option="P0") override
Specific drawing options can be used to paint a TGraph2D:
Definition: TGraph2D.cxx:740
This is the base class for the ROOT Random number generators.
Definition: TRandom.h:27
void SetHistTopMargin(Double_t hmax=0.05)
Definition: TStyle.h:369
Double_t y[n]
Definition: legend1.C:17
return c1
Definition: legend1.C:41
Double_t x[n]
Definition: legend1.C:17
Double_t ey[n]
Definition: legend1.C:17
Double_t ex[n]
Definition: legend1.C:17
Short_t Abs(Short_t d)
Returns the absolute value of parameter Short_t d.
Definition: TMathBase.h:123