Can TLegend object be added to a TMultiGraph object plotting？

[newconcept1979]

I want to add a TLegend object to a TMultiGraph object, but i seems not work, here is the key code:

    TLegend* lg1=new TLegend(0.1,0.7,0.3,0.9,"Scattering and Efficiency Correction");
    lg1->SetFillColor(0);
    lg1->AddEntry(mg1,"Cal Data");
    lg1->AddEntry(gr1,"Efficiency");
    lg1->AddEntry(gr2,"Correction");
    lg1->DrawClone("same");

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ROOT Version: 6.24/02
Platform: Ubuntu 20.04
Compiler: GCC 9.3.0

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[newconcept1979]

[Wile_E_Coyote]

It’s unclear what you do. Try:

TCanvas *c = new TCanvas("c", "c");
mg1->Draw("AL");
gr1->Draw("P");
gr2->Draw("P")'
lg1->Draw();
c->SaveAs("c.png");

[couet]

Add also:

  TLegend* lg1=new TLegend(0.1,0.7,0.3,0.9,"Scattering and Efficiency Correction");
    lg1->SetFillColor(0);
    lg1->AddEntry(mg1,"Cal Data");
    lg1->AddEntry(gr1,"Efficiency");
    lg1->AddEntry(gr2,"Correction");

Before drawing the legend.

You can also use BuildLegend instead.