TGraph zoom issues

ROOT
1

I have a canvas with a TGraph drawn. I would like to get its zoom ranges and apply to a next graph which will be drawn in the same canvas. It seems that I can get the ranges only with gPad.GetUymin/max(). GetMaximum() on graph returns the pre-zoom maximum of the graph, GetFirst/Last() on axis returns always 1 and so on…

However, I cannot find anywhere a method to set the Pad zooms, like SetUymin/max(). Setting TGraph.SetMaximum() would work, but then the values of min/max would be stored elsewhere then those accessible by gPad.GetUymin/max(). What should I do?

2

root.cern.ch/drupal/content/how-set-ranges-axis

3

Doesn’t work. I draw graph from the TTree, than try to use it, but no change. Somehow the Graph and what is drawn are living separate lives:

self.etosTree.Draw("avg_pc_data[" + str(pix_num) + "]:threshold[0]>>pixgraph(100, -1, -1, 100000, -1, -1)", "avg_pc_data[" + str(pix_num) + "]<0.1*100", "*")
ROOT.gPad.GetPrimitive("Graph").SetName("SCurveGraph1")
ROOT.gPad.GetPrimitive("SCurveGraph1").GetHistogram().SetMinimum(zoom_ymin)
ROOT.gPad.GetPrimitive("SCurveGraph1").GetHistogram().SetMaximum(zoom_ymax)
4

In case of a tree drawing, the axis are defined with a TH2F.
The graph is plotted on top of it as you can see from gPad->ls():

root [1] gPad->ls()
Canvas Name=c1 Title=c1 Option=
 TCanvas fXlowNDC=0 fYlowNDC=0 fWNDC=1 fHNDC=1 Name= c1 Title= c1 Option=
  OBJ: TList	TList	Doubly linked list : 0
   TFrame  X1= -4.500000 Y1=-4.500000 X2=5.000000 Y2=5.000000
   OBJ: TH2F	htemp	px:py : 1 at: 0x7fdc2c6f9df0
   OBJ: TPaveText	title  	X1= -0.414727 Y1=5.475000 X2=0.914727 Y2=6.128125
   OBJ: TGraph	Graph	Graph : 1 at: 0x7fdc2c7173c0
root [2]

To change the axis limits you should change htemp:

   ntuple->Draw("px:py");
   gPad->Update();
   TH2F *h = gPad->GetPrimitive("htemp");
   h->GetYaxis()->SetRangeUser(0.,1.);
   gPad->Modified();
5

Works, thank you!