Get y-axis tick positions

[fsili]

Dear ROOT experts,

I am trying to get the values at where Y-ticks are drawn. For example, let’s say I have a determined y-range and I have selected the number of Ndivisions to plot on the axis

yrange = [0, 2.2]
ndivisions = 403

Is there a way to get the y-values at which the ticks are drawn, and to know if they belong to the primary/secondary divisions? In this case, I want to obtain the following values:

y_primary   = [0, 1.0, 2.0]
y_secondary = [0.5, 1.5]

I went throught the TAxis and TGaxis documentation but I haven’t found anything. Maybe I missed it? Or at least, is this possible? The other alternative is to obtain the values by writing the code, but it seems quite complicated.

Thanks a lot in advance

Cheers,
Francisco

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ROOT Version: 6.28

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[bellenot]

I’m not sure it is possible, but I’m sure @couet knows

[couet]

Try this macro:

void get_main_labels() {

   float x1    = 0.214;
   float y1    = -0.1;
   float x2    = 2.6;
   float y2    = 6.3;
   int   ndivx = 10;
   int   ndivy = 5;
   int   i;

   TCanvas *C = new TCanvas();

   // Define the 2 axis
   TH1F *f = C->DrawFrame(x1, y1, x2, y2);
   f->GetXaxis()->SetNdivisions(ndivx);
   f->GetYaxis()->SetNdivisions(ndivy);

   printf("The labels on the X axis are:\n");
   int divxo    = 0;
   Double_t x1o = 0.;
   Double_t x2o = 0.;
   Double_t bwx = 0.;
   THLimitsFinder::Optimize(x1,x2,ndivx,x1o,x2o,divxo,bwx,"");
   Double_t xl = x1o;
   for (i = 0; i<=divxo; i++) {
      printf("xl[%d] = %g\n",i,xl);
      xl = xl + bwx;
   }

   printf("The labels on the Y axis are:\n");
   int divyo    = 0;
   Double_t y1o = 0.;
   Double_t y2o = 0.;
   Double_t bwy = 0.;
   THLimitsFinder::Optimize(y1,y2,ndivy,y1o,y2o,divyo,bwy,"");
   Double_t yl = y1o;

   for (i = 0; i<=divyo; i++) {
      printf("yl[%d] = %g\n",i,yl);
      yl = yl + bwy;
   }
}