RE: Drawing part of a TGraphErrors

From: Olivier Couet <Olivier.Couet_at_cern.ch>
Date: Tue, 20 Feb 2007 10:16:59 +0100

Dear Cecilie,  

Can you send me a small running example ? The few lines you sent before are not complete.  

Cheers, Olivier

---

From: Ann-Cecilie Larsen [mailto:a.c.larsen_at_fys.uio.no] Sent: Monday, February 19, 2007 7:31 PM
To: Olivier Couet
Cc: RootTalk
Subject: Re: [ROOT] Drawing part of a TGraphErrors

Dear Olivier,

1. feb. 2007 kl. 17.42 Olivier Couet wrote:

        May be something like that would be simpler:                   

	{
	   Int_t n=20;
	   Double_t x[n],y[n];
	   for (Int_t i=0; i < n; i++) {
	      x[i]=i*0.1;
	      y[i]=10*sin(x[i]+0.2);
	   }
	   TGraph *gr1 = new TGraph (n,x,y);
	   TAxis *axis = gr1->GetXaxis();
	
	   axis->SetLimits(0.,5.);                 // along X
	   gr1->GetHistogram()->SetMaximum(20.);   // along          
	   gr1->GetHistogram()->SetMinimum(-20.);  //   Y     
	
	   gr1->Draw("AC*");
	}
	

Thanks so much for your suggestion, but unfortunately it doesn't help me. The data file I am reading to get the TGraphErrors contains zeroes, and if I plot the whole graph also the zero points appear with markers. This I would like to avoid, and therefore I tried to use the DrawGraph function, which is perfect for a TGraph.

Cheers, Cecilie

---

        From: owner-roottalk_at_pcroot.cern.ch
[mailto:owner-roottalk_at_pcroot.cern.ch] On Behalf Of Ann-Cecilie Larsen

	Sent: Monday, February 19, 2007 5:24 PM
	To: RootTalk
	Subject: [ROOT] Drawing part of a TGraphErrors
	
	
	Dear Rooters, 

	I am trying to plot only a part of a graph with error bars using

the following statements in my macro:

// make graph

        TGraphErrors *gr_fg3 = new
TGraphErrors(n,energy,fg3,xerr,fgerr3); // for fg

// creating histogram (just for the axis)

	TH2F *h1 = new TH2F("h1"," ",10,0.0,8.0,10,0.0,1.0);
	h1->Draw(); // draw axis
	gr_fg3->SetMarkerStyle(21);
	gr_fg3->SetMarkerSize(0.6);
	gr_fg3.DrawGraph(8,&gr_fg3->GetX()[5],&gr_fg3->GetY()[5],"P");

// draw fg data

        But the error bars disappear in the pad... Is there another function than DrawGraph that should be used with the TGraphErrors?

        Cheers, Cecilie         

---

	Ann-Cecilie Larsen
	Oslo Cyclotron Laboratory (http://ocl.uio.no/)
	Department of Physics, University of Oslo
	P.O.Box 1048 Blindern
	N-0316 Oslo, Norway
	Phone: +47 22 85 64 63 Fax: +47 22 85 64 22
	E-mail: a.c.larsen_at_fys.uio.no
	====================================

Received on Tue Feb 20 2007 - 10:17:07 CET