Label pushed outside of canvas

[Viesturs]

I create a graph:

const double x[] = {0.0, 1.0};
const double y[] = {20000.0, 10000.0};
TGraph g(2, x, y);
g.GetYaxis() -> SetTitle("#frac{A}{B}");

When I draw it:

TCanvas c;
g.Draw("AP*");

the y axis label is pushed outside of the canvas:

How to fix this problem?

[couet]

It is because the axis labels are long and the title is automatically positioned to not overlap them. That was a recent request we had. Before the title would have overlapped the labels.

Do:

{
   const double x[] = {0.0, 1.0};  
   const double y[] = {20000.0, 10000.0};
   TGraph g(2, x, y);
   g.GetYaxis() -> SetTitle("#frac{A}{B}");
   g.GetYaxis() -> SetTitleOffset(1.);
   g.Draw("A*");
}

[Viesturs]

Now the result is:

Luckily the y axis title has not bumped into the axis label (20000).

[Viesturs]

If I set the y axis title as follows

g.GetYaxis() -> SetTitle("-2ln#frac{A}{B}");

the result is no longer acceptable:

Now I could ask the question again - how to fix the problem?

[Wile_E_Coyote]

{
  const double x[] = {0.0, 1.0};
  const double y[] = {20000.0, 10000.0};
  TGraph g(2, x, y);
  g.GetYaxis()->SetTitle("-2ln#frac{A}{B}");
  g.GetYaxis()->SetTitleOffset(5.);
  g.GetYaxis()->CenterTitle(kTRUE);
  g.GetXaxis()->SetTitle("#frac{A}{B}");
  g.GetXaxis()->SetTitleOffset(5.);
  g.GetXaxis()->CenterTitle(kTRUE);
  TCanvas *c = new TCanvas("c", "c");
  if (gPad) gPad->SetLeftMargin(0.5);
  if (gPad) gPad->SetBottomMargin(0.5);
  g.Draw("A*");
}

[couet]

{
   auto *c1 = new TCanvas();
   c1->SetLeftMargin(0.2);
   const double x[] = {0.0, 1.0};
   const double y[] = {20000.0, 10000.0};
   TGraph g(2, x, y);
   g.GetYaxis() -> SetTitle("-2ln#frac{A}{B}");
   g.Draw("A*");
}

[sbinet]

this all seems a bit fragile.

a probably better strategy would be for the ROOT painter to automatically compute the width+height needed for the X/Y axes, their ticks+ticks’ labels, reserve enough space for those, and then display the axis-label in the leftover space.
no user intervention needed.

(that’s what we do in gonum/plot…)

[couet]

@sbinet

no user intervention needed.

Yes that’s always the same discussion “automatic” vs “user control” …
If all is automatic there is no way to define precisely a plot ready for publication placing precisely all the elements.
We are now by default placing the Y axis title automatically and still there is cases like this one where adjustments are required. You suggest more automatic setting… thats all fine until somebody comes with a case where the automatic placements are not producing what he/she wants and we are back in the same situation …that’s a bit endless.

[sbinet]

yes, nature or nurture

still, there is a difference between having something automatic that automatically put overlaping glyphs (as is reported here) and something that doesn’t fit someone’s aesthetical taste.

[ksmith]

Another recent discussion about this:

Axis Label Placement

Continuing the discussion from Making sure axis label and title don't overlap: Ive had a user complain to me about the fact that some of the axis titles are now placed off the screen since version 6.10. This occurs when you have large numbers on the Y-axis, but was not evident in version 6.08 (although here you would have occasional overlap, but you could at least see the label.) Any suggestions on how to fine tune this algorithm, or automatically adjust the axis labels, or the size of the fram…

[Viesturs]

Besides

c1 -> SetLeftMargin(0.2);

one also needs to call

g.GetYaxis() -> SetTitleOffset(2.0);