I am trying to plot data from set of txt files and do a common fit using TMultiGraph Fit() The fit is valid and is also evident from the drawn fit function.
However, in the TLegend, box, the fit line does not appear. Can someone please help here
void do_fit()
{
auto*gr1 = new TGraph("fwhm_sqr.txt", "%lg %lg");
gr1->SetMarkerStyle(8);
gr1->SetMarkerColor(kRed);
auto *gr2 = new TGraph("fwhm_sqr.txt", "%lg %*lg %lg");
gr2->SetMarkerStyle(8);
gr2->SetMarkerColor(kBlue);
auto g = new TMultiGraph();
g->Add(gr1);
g->Add(gr2);
g->Draw("ap");
g->Fit("pol1") ;
gPad->BuildLegend();
gStyle->SetOptFit(111);
}
void do_fit()
{
auto*gr1 = new TGraph("fwhm_sqr.txt", "%lg %lg");
gr1->SetMarkerStyle(8);
gr1->SetMarkerColor(kRed);
auto *gr2 = new TGraph("fwhm_sqr.txt", "%lg %*lg %lg");
gr2->SetMarkerStyle(8);
gr2->SetMarkerColor(kBlue);
auto g = new TMultiGraph();
g->Add(gr1);
g->Add(gr2);
g->Draw("ap");
TF1 *f1 = new TF1("f1", "pol1");
f1->SetLineColor(kMagenta);
f1->SetTitle("whatever title you want to appear in legend");
f1->Draw("same");
g->Fit(f1);
gPad->BuildLegend();
}