RE: TH2F stats Access

From: Adam Roe <>
Date: Fri, 22 Sep 2006 10:00:58 +0200

This is what I got:

root [0] TH2F* h2Test = new TH2F("h2Test", "test of autoBin", 10, 0, 0, 10, 0,0);
root [1] h2Test->SetBinContent(7,12,2);
root [2] h2Test->SetBinContent(1,5,1);
root [3] h2Test->Draw();

<TCanvas::MakeDefCanvas>: created default TCanvas with name c1 Error in <TCanvas::Range>: illegal world coordinates range: x1=0.000000, y1=0.000000, x2=0.000000, y2=0.000000 Error in <TCanvas::RangeAxis>: illegal axis coordinates range: xmin=0.000000, ymin=0.000000, xmax=0.000000, ymax=0.000000

The plot shown has 2 entires in the stats, but none are shown. the other stats all say 0 as well. If it makes a difference, I am using CERN linux, and the release of root that is built with a recent CMS software package, CMSSW_0_9_0_pre2


-----Original Message-----
From: Rene Brun
Sent: Thu 9/21/2006 6:03 PM
To: Adam Roe
Cc: roottalk (Mailing list discussing all aspects of the ROOT system) Subject: Re: [ROOT] TH2F stats Access  

The looping to do this should be extremely simple (3 C++ lines), but you don't need to do this
for the goal that you want to achieve.
You should simply use the automatic binning facility of the histogramming package.Instead of

root [1] TH2F* h2Test = new TH2F("h2Test", "test of yMax", 10, 0, 10, -5, 20);


root [1] TH2F* h2Test = new TH2F("h2Test", "test of yMax", 10, 0, 0, 10,0,0);

Rene Brun

Adam Roe wrote:
> Hi all (again),
> I asked a question this morning, but i believe i phrased it wrong. I am trying to access the highest y-value in a data set which is in a histogram. Here is an explicit (trivial) example of what I am trying to do:
> root [1] TH2F* h2Test = new TH2F("h2Test", "test of yMax", 10, 0, 10, -5, 20);
> root [1] TH2F* h2Test = new TH2F("h2Test", "test of yMax", 10, 0, 10, -5, 20);
> root [2] h2Test->SetBinContent(1,1,1);
> root [3] h2Test->SetBinContent(3,5,2);
> root [4] h2Test->SetBinContent(4,41,3);
> And now i would like to call somethineg which returns 41, the maximum y value in h2Test. I would then use this to reset the yaxis range, so that this point is included.
> I cannot find a way to get this value. The looping is rather large and complicated, so i am trying to avoid filling a vector with x-y coordinates and then fidning the maximum value in it.
> This functionality is very simple for a TH1F. calling h1->GetMaximum() returns the highest y-value that is reached in h1. But i cannot get it to function for TH2F.
> Thanks,
> Adam
Received on Fri Sep 22 2006 - 10:01:09 MEST

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