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Reference Guide
SimpleFitting.C File Reference

Detailed Description

Create an exponential fitting The idea is to create a set of numbers x,y with the function x^3 and some noise from ROOT, fit the function to get the exponent (which must be near 3) and plot the points with noise, the known function and the fitted function.

TCanvas *SimpleFitting(){
TCanvas *c1 = new TCanvas("c1","Curve Fitting",700,500);
// draw a frame to define the range
// create the first plot (points with gaussian noise)
const Int_t n = 24;
//Generate the points along a X^3 with noise
TRandom rg;
for (Int_t i = 0; i < n; i++) {
x1[i] = rg.Uniform(0, 1);
y1[i] = TMath::Power(x1[i], 3) + rg.Gaus() * 0.06;
TGraph *gr1 = new TGraph(n,x1,y1);
// create the second plot
TF1 *f_known=new TF1("f_known","pow(x,3)",0,1);
TGraph *gr2 = new TGraph(f_known);
//passing data to Rfot fitting
r["x"]<<TVectorD(n, x1);
r["y"]<<TVectorD(n, y1);
//creating a R data frame
//fitting x and y to X^power using Nonlinear Least Squares
r<<"m <- nls(y ~ I(x^power),data = ds, start = list(power = 1),trace = T)";
//getting the exponent
Double_t power;
TF1 *f_fitted=new TF1("f_fitted","pow(x,[0])",0,1);
//plotting the fitted function
TGraph *gr3 = new TGraph(f_fitted);
//displaying basic results
TPaveText *pt = new TPaveText(0.1,0.6,0.5,0.9,"brNDC");
pt->AddText("Fitting x^power ");
pt->AddText(" \"Blue\" Points with gaussian noise to be fitted");
pt->AddText(" \"Red\" Known function x^3");
TString fmsg;
fmsg.Form(" \"Green\" Fitted function with power=%.4lf",power);
return c1;
int Int_t
Definition: RtypesCore.h:45
double Double_t
Definition: RtypesCore.h:59
@ kRed
Definition: Rtypes.h:66
@ kGreen
Definition: Rtypes.h:66
@ kBlue
Definition: Rtypes.h:66
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
Option_t Option_t TPoint TPoint const char x1
Option_t Option_t TPoint TPoint const char y1
TVectorT< Double_t > TVectorD
Definition: TVectorDfwd.h:23
ROOT R was implemented using the R Project library and the modules Rcpp and RInside
Definition: TRInterface.h:136
static TRInterface & Instance()
static method to get an TRInterface instance reference
virtual void SetFillColor(Color_t fcolor)
Set the fill area color.
Definition: TAttFill.h:37
virtual void SetMarkerColor(Color_t mcolor=1)
Set the marker color.
Definition: TAttMarker.h:38
virtual void SetMarkerStyle(Style_t mstyle=1)
Set the marker style.
Definition: TAttMarker.h:40
virtual void SetMarkerSize(Size_t msize=1)
Set the marker size.
Definition: TAttMarker.h:41
virtual void SetTextAlign(Short_t align=11)
Set the text alignment.
Definition: TAttText.h:42
The Canvas class.
Definition: TCanvas.h:23
1-Dim function class
Definition: TF1.h:213
virtual void SetParameter(Int_t param, Double_t value)
Definition: TF1.h:639
A TGraph is an object made of two arrays X and Y with npoints each.
Definition: TGraph.h:41
A TMultiGraph is a collection of TGraph (or derived) objects.
Definition: TMultiGraph.h:34
A Pave (see TPave) with text, lines or/and boxes inside.
Definition: TPaveText.h:21
virtual TText * AddText(Double_t x1, Double_t y1, const char *label)
Add a new Text line to this pavetext at given coordinates.
Definition: TPaveText.cxx:187
void Draw(Option_t *option="") override
Draw this pavetext with its current attributes.
Definition: TPaveText.cxx:238
This is the base class for the ROOT Random number generators.
Definition: TRandom.h:27
virtual Double_t Gaus(Double_t mean=0, Double_t sigma=1)
Samples a random number from the standard Normal (Gaussian) Distribution with the given mean and sigm...
Definition: TRandom.cxx:274
virtual void SetSeed(ULong_t seed=0)
Set the random generator seed.
Definition: TRandom.cxx:608
virtual Double_t Uniform(Double_t x1=1)
Returns a uniform deviate on the interval (0, x1).
Definition: TRandom.cxx:672
Basic string class.
Definition: TString.h:136
void Form(const char *fmt,...)
Formats a string using a printf style format descriptor.
Definition: TString.cxx:2319
TPaveText * pt
return c1
Definition: legend1.C:41
const Int_t n
Definition: legend1.C:16
static constexpr double mg
LongDouble_t Power(LongDouble_t x, LongDouble_t y)
Returns x raised to the power y.
Definition: TMath.h:719
Omar Zapata

Definition in file SimpleFitting.C.