Error on SetLogy for two plots with SetRangeUser

[NgJunKai]

i got Error in <THistPainter::PaintInit>: Cannot set Y axis to log scale when i did the following:
(try to uncomment the SetRangeUser() line to see the error.

f1 = r.TF1("f1","landau")
f1.SetParameters(1e6,2,3)

obj1 = r.TH1D("h1","h1",200,0,3)
obj1.SetLineColor(2)
obj2 = r.TH1D("h2","h2",200,0,3)

obj1.FillRandom("f1",1000000)
obj2.FillRandom("landau",1000000)

c = r.TCanvas("c","c",800,800)
c.SetLogy()
obj1.Draw("")
# obj1.GetYaxis().SetRangeUser(0,7500)
obj2.Draw("same")
c.Draw()

any suggestion ?

---

ROOT Version: 6.24 & 6.28.06
_Platform:(conda) Centos7 & MacOS ventura
Compiler: Not Provided

---

[dastudillo]

Without knowing what obj1 and obj2 are, we cannot tell, so it’s better to post code that can be run and that reproduces the problem.
The following works:

import ROOT as r
import math
c = r.TCanvas("c","c",800,800)
c.SetLogy()
n = 20
g1 = r.TGraph(n)
g2 = r.TGraph(n)
for i in range (n):
    g1.SetPoint(i,i,10*math.sin(i*0.1+0.2)-4)
    g2.SetPoint(i,i,5*math.sin(i*0.1+0.2))

g1.Draw("AC*")
g2.Draw("C*")
c.Draw()

even swapping the drawing order of g1 and g2 (note that g1 has some negative y values, and it still works with log, at least on root 6.26/10). And by the way, you don’t need that c.Draw(), as g1 and g2 are already drawn on c in this case, given your code.

[NgJunKai]

the two obj are just randomly filled histograms

[dastudillo]

Well, my example works as expected, as I mentioned, so it may be a problem with your objects. Can you post the full code that shows your issue? If my example doesn’t work for you then you have a different problem, maybe try resintalling root, or a newer version.

[NgJunKai]

Ok, i have rephrased my question… after finding that this is something to do with the SetRangeUser(). try to reproduce with the corresponding line commented out / commented.

[couet]

Log is not defined for 0.
do:

void ng() {
   auto f1 = new TF1("f1","landau");
   f1->SetParameters(1e6,2,3);
   auto h1 = new TH1D("h1","h1",200,0,3);
   h1->SetLineColor(kRed);
   auto h2 = new TH1D("h2","h2",200,0,3);

   h1->FillRandom("f1",1000000);
   h2->FillRandom("landau",1000000);

   auto c = new TCanvas("c","c",800,800);
   c->SetLogy();
   h1->Draw();
   h1->GetYaxis()->SetRangeUser(0.01,7500);
   h2->Draw("same");
}