Color Axis Label Size

ROOT
1

Hello,

I am plotting a 2D histo w/ colz option. The labels on the color axis however are too big. I can easily change their size in the interactive pad way, but would like to have my program do this automatically. All that i really need to do is to get the TPaletteAxis from the canvas which is automatically names “palette”. However i tried :

TPaletteAxis *pal = gPad->FindObject(“palette”);

which runs error free but gives an empty pointer of that class, to which i cannot perform the necessary action.

There must be an obvious way that i can get this palette in order to modify it that i am missing somewhere.

If any one could help me, i would really appreciate it.

Thanks in advance,

Mitch C.

2

The palette is connected to the histogram list of functions. See class description of TPaletteAxis at:
root.cern.ch/root/htmldoc/TPaletteAxis.html

To change the label size, do:
TPaletteAxis *pal = h->GetListOfFunctions()->FindObject(“palette”);
pal->GetAxis()->SetLabelSize(0.03);

Rene

3

thanks a lot

mitch c.

4

Actually, i had though that this worked, because i tested it in root and performed what i wanted.

However, I had forgotten (and forgotten to mention) , that i have to run root in batch mode. This way doesnt seem to work for root in batch mode.

example:
"
root -b

root: TH2F *h = new TH2F("","",10,0,10,10,0,10);
root: h->Fill(3,3);
root: h->Draw(“colz”);
root: TPaletteAxis pal = (TPaletteAxis) (h->GetListOfFunctions()->FindObject(“palette”));
root: pal->GetAxis()->SetLabelSize(.3);
Error: illegal pointer to class object pal 0x0 972 FILE:(tmpfile) LINE:1
*** Interpreter error recovered ***
"

it seems that the palette gets returned as a blank pointer of type TPaletteAxis. I guess that the color axis palette is not accesible in the same when when running in batch mode.

Sorry for wasting your time with the first question, i obviously didn’t know what i was talking about.

Is there a way to do this?
If anyone could help it would be really appreciated.

Thanks ,

Mitch C.

5

I suggest you read the chapter about Graphics in the Users Guide or at least
root.cern.ch/root/HowtoDraw.html
The objects such as the TPaveStats box or the TPaletteAxis are created only when effectively painting the histogram. Simply calling Draw adds a reference to the list of primitives in the pad.
Before accessing your TPaletteAxis object, you should call
mycanvas->Update();
In an interactive session, this is automatic when you press CR

Rene