Setup of TAxis after zoom

ROOT
1

Hello,

I have some time dependant data displayed in a TGraph. I created a function which makes sure that the ticks gets on rounded seconds ( for example at 1s , 2s , … and not 1.1s, 2.2s, …)
It is mainly to avoid the ticks labels with ms (such as “10:00:00s15”) when ticks are placed at non-integer seconds.

TGraph* xaxis_time(TGraph *gr)
{
  gr->GetXaxis()->SetTimeDisplay(1);
  time_t xmin=floor(gr->GetXaxis()->GetXmin());
  time_t xmax=ceil(gr->GetXaxis()->GetXmax());
  gr->GetXaxis()->SetLimits(xmin,xmax); 	//set rounded limits
  UInt_t xticks_interval=ceil((xmax-xmin)/10.);//interval between ticks to get ~10 ticks
  UInt_t ndiv=((xmax-xmin)/xticks_interval);	//number of ticks 
  gr->GetXaxis()->SetNdivisions(-ndiv); 		//set number of ticks
  gr->GetXaxis()->SetLabelSize(0.03);
  gr->GetXaxis()->SetTimeFormat("%H:%M:%S");
  return gr;
}

However whenever the axis is zoomed, that setup is obviously lost.
Is there a way to call that function each time the axis get zoomed ?
Otherwise is there a way to insure that the ticks get automatically placed on rounded time ?

2

Yes, you can add a TExec in your pad:

root.cern.ch/doc/master/classTExec.html

3

Thank you very much, it looks it is exactly what I needed !
However I have trouble to make it to work. When I do

TGraph *gr_spectra;
TExec *setup_xaxis_time;
gr_spectra=new TGraph(nentries_ploted,this->timestamp_float+first_entry,this->data+first_entry);
setup_xaxis_time= new TExec("xaxis_time","xaxis_time(gr_spectra)");
gr_spectra->GetListOfFunctions()->Add(setup_xaxis_time);
gr_spectra->Draw("AL*");

I get the error: "Error: Symbol gr_spectra is not defined in current scope ".
However from the 1st example in the link you gave me, it looked like local variables could be used within TExec.

4

can you send a small running reproducer ?

5

here is the content of file test.C

void plot(void){
  TGraph *gr_spectra;
  TExec *setup_xaxis_time;
  TExec *test;
  const Int_t npoints=3;
  Double_t xaxis[npoints] = {1455805368,1455805369,1455805370};
  Double_t yaxis[npoints] = {10.,20.,30.};
  gr_spectra=new TGraph(npoints,xaxis,yaxis);
  test= new TExec("test","test()");
  setup_xaxis_time= new TExec("xaxis_time","xaxis_time(gr_spectra)");
  gr_spectra->GetListOfFunctions()->Add(test);
  gr_spectra->GetListOfFunctions()->Add(setup_xaxis_time);
  gr_spectra->Draw("AL*");
}

TGraph* xaxis_time(TGraph *gr)
{
  gr->GetXaxis()->SetTimeDisplay(1);
  gr->GetXaxis()->SetTimeFormat("%H:%M:%S");
  return gr;
}

void test(void)
{
  cout<<"it works"<<endl;
}

below is the output when run with root -l test.C:
Processing plot.C…
Info in TCanvas::MakeDefCanvas: created default TCanvas with name c1
it works
Error: Symbol gr_spectra is not defined in current scope (tmpfile):1:
*** Interpreter error recovered ***

6

May be this:


TGraph *gr_spectra;

void renier(void){
  TExec *setup_xaxis_time;
  TExec *test;
  const Int_t npoints=3;
  Double_t xaxis[npoints] = {1455805368,1455805369,1455805370};
  Double_t yaxis[npoints] = {10.,20.,30.};
  gr_spectra=new TGraph(npoints,xaxis,yaxis);
  test= new TExec("test","test()");
  setup_xaxis_time= new TExec("xaxis_time","xaxis_time()");
  gr_spectra->GetListOfFunctions()->Add(test);
  gr_spectra->GetListOfFunctions()->Add(setup_xaxis_time);
  gr_spectra->Draw("AL*");
}

void xaxis_time()
{
  gr_spectra->GetXaxis()->SetTimeDisplay(1);
  gr_spectra->GetXaxis()->SetTimeFormat("%H:%M:%S");
}

void test(void)
{
  cout<<"it works"<<endl;
}
7

It works, thank you.