#include"TCanvas.h"
#include"TF1.h"
#include"TROOT.h"
#include"TMath.h"
#include"TGraph.h"


void test()

{
  
TCanvas* c1 = new TCanvas("c1","Graph");

float x,y;

TGraph *g = new TGraph("test2.txt");
 TF1 *f1 = new TF1("f1","[0]*x+[1]",0.,5.);

f1->SetParameters(5,0);
g->SetMarkerStyle(3);
g->Fit("f1");
g->Draw("ap");

}