SetRangeUser doesn't work well

ROOT
2

Try:
MyGraph->GetXaxis()->SetLimits(xmin, xmax);
MyGraph->GetYaxis()->SetRangeUser(ymin, ymax);
or:
MyGraph->GetXaxis()->SetLimits(xmin, xmax);
MyGraph->GetHistogram()->SetMinimum(ymin);
MyGraph->GetHistogram()->SetMaximum(ymax);

See also [url]Drawing a TGraphAsymmErrors and [url]SetAxisRange(0.0,1.0,"Y"); is ineffective