Adding a value on an axis

ROOT
1

Hi,

I drew multiple TH2 histograms in a divided TCanvas, which looks like this :

I have 3 little problems with it. I tried different things to solve them but nothing worked so far.

  1. My main problem is I want to add a specific value on the x-axis. Ideally, I’d want to add for example the number “34” on the x-axis (at the right place on the x axis) and written in red characters. I tried to play with the “bin” functions but nothing worked. Is there a simple way to do it ?

  2. I can’t change the size of the title for the TH2 histograms (“a” and “b” on the image). I used the SetTitleSize() method on the TH2 Histograms but it didn’t work. I also used the Update() method afterwards, just in case.

  3. I put a title on the TCanvas but it doesn’t appear. I also tried to put a top margin on TCanvas (with the SetTopMargin() method) but it didn’t work either.

Thanks for your help.

2

You should use TText to put this exact value at the right place. Drawing the text in the histogram coordinates (default) should put it automatically at the right place.

gStyle->SetTitleFontSize();

Send a small running macro reproducing this problem.

3

Exactly what I was looking for. Thank you !

Thank you again !

Send a small running macro reproducing this problem.[/quote]
Maybe the title of a TCanvas is not supposed to be seen but here is an example of a macro :

[code]{
TCanvas* canvas = new TCanvas(“Canvas”, “CanvasTitle”, 0, 0, 500, 500);

canvas->SetTopMargin(0.1);

canvas->Divide(1,2);
canvas->cd(1);

TH1F* hist1 = new TH1F(“Hist1”, “Title1”, 1, 0, 100);
hist1->SetFillColor(kGray);
for (int i = 0; i < 4; ++i) {
char dataName[50];
sprintf(dataName, “Data%d”, i);
hist1->Fill(dataName, 10 + 50*i);
}
hist1->Draw(“bar”);
} [/code]

I create a canvas, set a topMargin (of 10% if I understand correctly), then divide the Canvas, and draw a (non important) histogram in the first part of the canvas.
My problems with this are :

  • the title of the TCanvas is not displayed
  • the margin I tried to create for the Canvas is not created either

But again, maybe I’m trying to do something unintended.

4

Oh OK… I see what you mean now. No, the canvas title is not intended to be seen. It defines the tittle which appears on the window title bar. If you need a global title somehow, you should add an other TPaveText.

5

Ok I’ll do that. Thank you again !