Get mean, max, min y value for a specific range on x-axis for TGraphErrors

ROOT
4

Hi again @NgJunKai,

thank you for the reproducer.

What you are seeing for GetMaximum() is expected. It was already discussed in the forum post here: TGraph GetMaximum() GetMinimum().

The suggested solution is to use ROOT::TMath class, which would look like this if I indeed set the range to be between 3 and 7:

import ROOT 

func = ROOT.TF1("func","[0]*x + [1]")
func.SetNpx(1000)
func.SetParameters(2., 1.)

gr = ROOT.TGraph()

for i in range(3,8):
    gr.SetPoint(gr.GetN(), i, func.Eval(i))

print(ROOT.TMath.MaxElement(gr.GetN(),gr.GetY())) # gives 15 as expected
print(ROOT.TMath.MinElement(gr.GetN(),gr.GetY())) # gives 7 as expected

You can explore more of the ROOT::TMath class if you need other quantities, ROOT: TMath Namespace Reference and more generally the Math class is documented here ROOT: Math.

Cheers,
Marta

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