Hi Michael, Move the line mg->GetXaxis()->SetTitle("ms"); after mg->Draw The axis object is only created when painting the graph. I already changed TGraph to avoid this problem and forgot to make the same change to TMultiGraph. Rene Brun On Sat, 1 Mar 2003, Michael T. Gericke wrote: > > Hi ROOTers, > > I am using the TMultiGraph Class in the following way: > > TMultiGraph *mg = new TMultiGraph(); > mg->SetTitle("Lock-In Amplifier Technique Signals"); > mg->GetXaxis()->SetTitle("ms"); > mg->Add(gr1); > mg->Add(gr2); > mg->Add(gr3); > mg->Draw("ALP"); > > > When I run my file on the root command line, I get the > following error: > > Error: illegal pointer to class object GetXaxis() 0x0 138 > FILE:Rot_Src_Scope_Out.C LINE:107 > > I know that this refers to the line "mg->GetXaxis()->SetTitle("bla")", > because if I remove it the error doesn't come up. > > Does anyone know how to set the axis titles for a TMultiGraph? > > Thanks, > > Michael Gericke >
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