Setting x and y range on a multigraph

ROOT
1

Hello,
I am trying to set x and y range on a multigraph and am having problems. Sometimes when the graph is drawn, the x-range is correct (from -4.5 to 0.5) while other times it is drawn from 0 to some very large number. The chunk of code looks something like this

[code]
mg5->SetTitle("Vgs -0.8V");
mg5->Draw("AP");

mg5->GetXaxis()->SetTitle("Gate-to-Drain Voltage (V)");
mg5->GetYaxis()->SetTitle("Cgs+Cgd (pF)");
mg5->GetXaxis()->CenterTitle();
mg5->GetYaxis()->CenterTitle();
mg5->GetXaxis()->SetRangeUser(-4.5,0.5);
mg5->GetYaxis()->SetRangeUser(35.,80.);
mg5->GetXaxis()->SetLimits(-4.5,0.5);
gPad->Modified();[/code]

It is interesting to note that trying to perform a SetRangeUser on the graph through the GUI works sometimes but not others. The y-axis always appears to be drawn correctly. What is the correct way to set the range on an axis?
[/code]

2

The purpose of a TMultiGraph is to compute automatically the x and y boundaries. If you want to impose your own boundaries, you can
-call pad.DrawFrame(xmin,ymin,xmax,ymax)
or
-create a TH2F empty object, draw it (and/or set iits axis titles)
-superimpose your TMultiGraph

Rene