exemplo_MG()
{
  MG* g = new MG("fit.dat","%lg %lg %lg");  
  g->Draw("a p");

  TF1* f = new TF1("funcao","[0]/(x*[1]*sqrt([2]^2+(x*[3]-1/(x*[1]))^2))",3000,7000);
  f->SetParameters(5,1e-6,5,30e-3);  
  g->Fit(f);
  
  MG* r = g->residuos(f,true);
  
  MG* c1 = g->curvaChi2(f, 2, 0, 20, true);

}