How to print out my fit result on the plot? Here is my program below. And I cannot find the error

ROOT
1 
#include "TCanvas.h"
#include "TROOT.h"
#include "TGraphErrors.h"
#include "TF1.h"
#include "TFitResultPtr.h"
#include "TFitResult.h"

 void plot()
 {
 gStyle->SetOptTitle(1); 
 gStyle->SetOptStat(111111);
 gStyle->SetOptFit(1111);
 gStyle->SetStatBorderSize(0);
 gStyle->SetStatX(.89);
 gStyle->SetStatY(.89);
 auto c = new TCanvas();
 TGraphErrors graph("./ed.txt","%lg %lg");
 graph.SetTitle("Experimental Data;Energy(keV);Resolution");
 graph.SetMarkerStyle(5);
 graph.SetMarkerColor(kBlue);
 graph.DrawClone("AP");
 TF1 f("Power law","[0]*x**(-0.5)",0.,400.);
 f.SetLineColor(kRed); 
 f.SetLineStyle(1);
 f.SetLineWidth(2);
 graph.Fit(&f);
 f.DrawClone("Same");
 TFitResult(&f);
 TFitResult::Print();
 c->Print("graph_with_law.pdf");
 }
 
 int main(){
       plot();
    }
2

The argument of Fit is the name of the function, i.e. “Power law” in your case.

3

graph.Fit(&f); graph.Draw("AP");

4

Thank you very much! The problem has been solved. But I do not understand it. Did you mean the function “Draw” can print the fit result? And what’s meaning of the parameter “Prob”?

5

Yes, see the plot you obtain.