Constant 2d histogram: empty?

ROOT
1

hi,
I am doing the following

TH2F* myhist = new TH2F("myhist","myhist",2,0,2,2,0,2) root [3] myhist->Fill(0.5,0.5) (Int_t)(5) root [4] myhist->Fill(0.5,1.5) (Int_t)(9) root [5] myhist->Fill(1.5,0.5) (Int_t)(6) root [6] myhist->Fill(1.5,1.5) (Int_t)(10) root [7] myhist->Draw()
and when I look at the resulting histogram it looks EMPTY.
This can be a problem when tryoing to check whether the histo is filled by eye, of cousre one can check the statistics, but one can also wonder whether there is a bug in the way his histo is filled.
Plotting the histo with “colz” does not help. One needs to use “lego”.
Is this a default? It would be nice to have the “colz” plot set to a single color with a palette (not empty) showing only one value.
This has use cases for plots that are expected to be uniform (for instance in calorimetry plots showing cells read-out at the hardware level).

2

Yes, your histogram is uniform and in that case several plotting techniques do not display anything. In fact all those using a mapping of a graphics attribute (color, etc…) to the difference between the maximum and the minimum of the histogram. In the case of “COL” the method painting the color plot simply exit when zmax-zmin <= 0 . In the case of the scatter plot I see there is some code in the painting method which looks like dealing with your question. But it does not seems to work. I will investigate. Note that the option TEXT may be the use in such case. It plots the contain of the bin.

3

You can do:

myhist->Draw("scat=10000");

as explained here:
root.cern.ch/root/html/THistPainter.html#HP11