Histogram Bin Labels

ROOT
1

I would like to change/set the label of a particular histogram bin (say, the first one).
I know about
th1->GetXaxis()->SetBinLabel(0,“mylabel”)
However, once I perform this function call, all other bin labels disappear. I assume this has to do with the fact that the histogram switches to “alphanumeric mode” (whatever that means in detail).
What I would like to do is the following:
Change a single bin label to some expression (say, “#infty”), but leave alone the rest of the bin labels, that is, having them drawn as-usual without interfering with them in any way.

Is this possible? If so, what do I need to do?

Regards,
Carsten

PS: I have also thought about simply adding a TLatex to the canvas - the problem here being that I would then need to propagate this TLatex object through the whole production chain until the very end, when the histogram is drawn - plus, I would need to calculate the coordinates correctly, which I don’t know how to do. I was hoping for a possiblity to save the bin label information within the histogram object in a way that all Style changes are automatically and consistently applied to all bin labels (including my selfmade one).

2

You cannot mix alphanumeric and numeric labels. A soon as you set one label your histogram turns into an alphanumeric one and then you have to define all the labels the same way.

3

Ok, thanks for letting me know. However, this is of course a bit of a letdown.
Can you point me towards the location in the root source code where the bin/tick labels are automatically computed (when not set)? I could maybe copy that function and thus set all the other labels manually.

Since all this just boils down to the fact that I want to mark the underflow bin to be “special” (and make this fact easily recognizable when looking at the plot), I could alternatively do this by painting it on the other side of the axis. Is there an easy way to shift the axis to a different position of the plot? (I know about the X+/- Y+/- Draw options, but I would like to have the axis mid plot, on the right side of the first bin).

Regards,
Carsten

4

root.cern.ch/root/html534/TGaxis … :PaintAxis

In that case just add a TLatex or a TText at the right place.