void grapherrorfit()
{




TFile *_file1 = new TFile("~/Desktop/grapherror.root","READ");

TGraphErrors *g;

g = (TGraphErrors*)_file1->Get("g1_MMGA09L1");




auto *expfunc = new TF1("Exponential fit","[0]+[1]*exp(-x*[2])",0,500); 

expfunc->SetParameters(200,7e03,0.01);

g->Fit(expfunc,"RMS+");

g->Draw("AP");

expfunc->Draw("SAME");

double * p = expfunc->GetParameters();

cout << p[0] << " " << p[1] << "   " << p[2] << endl;

_file1->Close();




}