Get rid of line between TGraph points

ROOT
1

I attach the output of my current code, where there is a line connecting two sets of data points (one set is at x=620, one at x=1000).

My code reads:

g = ROOT.TGraph(len(exp_array),exp_array,dt_array)
g.SetMarkerStyle(1)
g.SetMarkerSize(1)
g.Draw(“AP”)

I looked (root.cern.ch/doc/master/classTGraphPainter.html) for which draw option to choose, and “AP” seems to be what I want.

I think that since I am using PyROOT, its possible that only some of the draw options are supported ("*", for example).

Does anybody know how to get rid of this line connecting two sets of data points?

tgraph1.png1037×557 5.36 KB

2

The option “AP” will draw your graph with Points only. Do you have a more complete script showing the problem ?

1 Like
3

Here is a sample script with the two text files

run like this:

$ python tgraphex.py --filename 1000.txt 620.txt
1000.txt (351 KB)
620.txt (527 KB)
tgraphex.py (2.18 KB)

4

Yes I see this line … What about if you use a simpler script.
Like the following one:

void graph() {
   const Int_t n = 20;
   Double_t x[n], y[n];

   for (Int_t i=0;i<n;i++) {
     x[i] = i*0.1;
     y[i] = 10*sin(x[i]+0.2)-5;
   }

   TGraph *gr = new TGraph(n,x,y);
   gr->SetMarkerStyle(20);
   gr->Draw("AP");
}

For me it gives only dots.

5

Can you give me a similar code to try with Python? It works fine for me in C++ (I see the dots)

6

you can just take your initial script as example and produce a translation of the simple example .
even do a more simple one:

void graph() {
   TGraph *gr = new TGraph();
   gr->SetPoint(0,0.,0.);
   gr->SetPoint(1,1.,1.);
   gr->SetPoint(2,2.,2.);
   gr->SetPoint(3,3.,3.);
   gr->SetMarkerStyle(20);
   gr->Draw("AP");
}
7

Sure, I just think some things are getting lost in my translation from C++ to Python (I’m new at coding). Have you been able to write an example in Python that produces the dots? I have tried and have not been able to, even with your simpler examples in C++.

8

this one produces dot:

from ROOT import *

c = TCanvas("c","c")

gr = TGraph()
gr.SetPoint(0,0.,0.)
gr.SetPoint(1,1.,1.)
gr.SetPoint(2,2.,2.)
gr.SetPoint(3,3.,3.)
gr.SetMarkerStyle(20)
gr.Draw("AP")

c.Print("c.pdf")