pyROOT x axis labels and ticks in multiple of of 512 (0, 512,1024,,..4096)

Newbie
,
1

I am a newbie and using pyROOT as I am more comfortable with Python. I have a TGraph object with a TF1 fit (linear). My x-axis ticks should be linear, and in multiples of 512 (digital-to-analog converter counts, 0 to 4095.). It should look like 0, 512, 1024, 1536, … 4096. But by default, it is in multiples of 500. Is there any way to change the default ticks? ChatGPT isn’t very helpful.

ROOT Version: 6.28
Platform: Ubuntu 23.04
Compiler: python3 + pyROOT

2

Welcome to the ROOT Forum!
Maybe @couet can help

3

Such axis labeling will not be easy to obtain automatically. Maybe you can get some inspiration from the following example:

void graphtext3() {
   TCanvas *c = new TCanvas("c","A Simple Graph with labels on points",700,500);

   const Int_t n = 10;
   TGraph *gr = new TGraph(n);
   gr->SetTitle("A Simple Graph Example with Text");
   gr->SetMarkerStyle(20);

   TExec *ex = new TExec("ex","DrawText();");

   gr->GetListOfFunctions()->Add(ex);

   Double_t x, y;
   for (Int_t i=0;i<n;i++) {
      x = i*0.1;
      y = 10*sin(x+0.2);
      gr->SetPoint(i,x,y);

   }

   gr->Draw("ALP");
   gr->GetXaxis()->SetLabelSize(0);
   gr->GetXaxis()->SetTickLength(0);
}


void DrawText()
{
   Int_t i,n;
   Double_t x,y;
   TLatex *t;
   TLine *l;

   TGraph *g = (TGraph*)gPad->GetListOfPrimitives()->FindObject("Graph");
   double ymin = g->GetHistogram()->GetMinimum();
   double ymax= g->GetHistogram()->GetMaximum();
   double dy = (ymax-ymin);
   n = g->GetN();
   for (i=0; i<n; i++) {
      g->GetPoint(i,x,y);
      t = new TLatex(x, ymin-0.03*dy, Form("%4.2f",x));
      t->SetTextSize(0.025);
      t->SetTextFont(42);
      t->SetTextAlign(21);
      t->Paint();
      l = new TLine(x,ymin,x,ymin+0.03*dy);
      l->Paint();
   }
}