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fit2d.C
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1/// \file
2/// \ingroup tutorial_fit
3/// \notebook -js
4/// Example illustrating how to fit a 2-d histogram of type y=f(x)
5///
6/// \macro_image
7/// \macro_output
8/// \macro_code
9///
10/// \author Rene Brun
11
12void fit2d()
13{
14 // generate a 2-d histogram using a TCutG
15 const Int_t n = 6;
16 Float_t x[n] = {0.092,0.83,0.94,0.81,0.12,0.1};
17 Float_t y[n] = {0.71,9.4,9,8,0.3,0.71};
18 TCutG *cut = new TCutG("cut",n,x,y);
19 TH2F *h2 = new TH2F("h2","h2",40,0,1,40,0,10);
20 Float_t u,v;
21 for (Int_t i=0;i<100000;i++) {
22 u = gRandom->Rndm();
23 v = 10*gRandom->Rndm();
24 if (cut->IsInside(u,v)) h2->Fill(u,v);
25 }
26 TCanvas *c1 = new TCanvas("c1","show profile",600,900);
27 c1->Divide(1,2);
28 c1->cd(1);
29 h2->Draw();
30 c1->cd(2);
31
32 //use a TProfile to convert the 2-d to 1-d problem
33 TProfile *prof = h2->ProfileX();
34 prof->Fit("pol1");
35}
36
int Int_t
Definition RtypesCore.h:45
float Float_t
Definition RtypesCore.h:57
R__EXTERN TRandom * gRandom
Definition TRandom.h:62
The Canvas class.
Definition TCanvas.h:23
Graphical cut class.
Definition TCutG.h:20
virtual Int_t IsInside(Double_t x, Double_t y) const
Return 1 if the point (x,y) is inside the polygon defined by the graph vertices 0 otherwise.
Definition TGraph.cxx:1908
virtual TFitResultPtr Fit(const char *formula, Option_t *option="", Option_t *goption="", Double_t xmin=0, Double_t xmax=0)
Fit histogram with function fname.
Definition TH1.cxx:3892
virtual void Draw(Option_t *option="")
Draw this histogram with options.
Definition TH1.cxx:3073
2-D histogram with a float per channel (see TH1 documentation)}
Definition TH2.h:251
TProfile * ProfileX(const char *name="_pfx", Int_t firstybin=1, Int_t lastybin=-1, Option_t *option="") const
Project a 2-D histogram into a profile histogram along X.
Definition TH2.cxx:2001
Int_t Fill(Double_t)
Invalid Fill method.
Definition TH2.cxx:294
Profile Histogram.
Definition TProfile.h:32
virtual Double_t Rndm()
Machine independent random number generator.
Definition TRandom.cxx:552
return c1
Definition legend1.C:41
Double_t y[n]
Definition legend1.C:17
Double_t x[n]
Definition legend1.C:17
const Int_t n
Definition legend1.C:16