Online Display

ROOT
1

Hello,

I tried to write an online display for a TGraph. It is no problem to draw the data periodically. But when I zoomed the TGraph and then the new data are displayed the graph is unzoomed automatically. I want only the data to be changed but not the displayed range of the graph. Thus one should see the points moving in the zoomed graph. To solve the problem I miss something like GetRangeUser of TAxis (according to SetRangeUser). Does anyone can help me?

2

You should call TGraph::Draw again and again, just gPad->Modified();
gPad->Update();

Rene

3

Hello,

following up this old thread, I actually have a similar problem. However, in my case, I would like to set the range of a graph (TAxis->SetRangeUser(…)) based on the currently set range, i.e. I have to access the currently displayed axis limits. Something like TAxis->GetRangeUser() does not seem to exist and the only workaround I found up to know is

GetXaxis()->GetBinLowEdge(GetXaxis()->GetFirst());

for the lower limit, for example. However, this seems rather clumsy and only approximate to me. What would be the correct way to achieve this?

Thanks in advance!

4

Could you post the shortest possible RUNNING script showing your problem?

Rene

5

Well, it is not really a problem which I can show to you in a script. It was rather a question:

How can I access the currently displayed access range of a TGraph?

6

Before calling TGraph::GetXaxis() you must force the painting of the canvas

canvas->Update(); mygraph->GetXaxis()->...
Rene