[ROOT] Setting axis limits for TF1 ?

From: David d'Enterria (denterria@nevis.columbia.edu)
Date: Sun Oct 06 2002 - 04:57:09 MEST 

Hello ROOTers,

I'm trying to change the scale the x-axis of a given function using 
 f1->GetHistogram()->GetXaxis()->SetLimits(a,b) without success, though 
randomly filling a histogram with the function and doing 
h1->GetXaxis()->SetLimits(a,b) does work (see simplified macro attached) ...

void test_axis_limits()
{

  TF1 *haged = 0;
 
  Double_t ptmin = 1.;
  Double_t ptmax = 5.;
  Double_t A = 330; // mb/(GeV/c)^2
  Double_t p0 = 1.72;
  Double_t n = 12.4;
  Double_t sqrt_s = 130.;
  Double_t pt2xt = 2./sqrt_s;
 
  TCanvas *c4 = new TCanvas("pp_130","pp_130",600,600);
  c4->SetLogy();
 
  haged = new TF1("haged","[0]*([1]/(x+[1])^[2])", ptmin, ptmax);
  haged->SetParameters(A, p0, n);
  haged->SetLineWidth(1); 
  haged->Draw("");
 
  haged->GetHistogram()->GetXaxis()->SetLimits(pt2xt*ptmin, pt2xt*ptmax); 
  haged->Draw("");
  //c4->SetLogx();
  c4->Update();

  // Now let's try with a histogram ...
 
  TCanvas *c5 = new TCanvas("hpp_130","hpp_130",600,600);
  c5->SetLogy();
 
  TH1F *hhag = new TH1F("hhag","hhag",100,ptmin,ptmax);
  hhag->FillRandom("haged",1000000);
  hhag->Draw();
  hhag->GetXaxis()->SetLimits(pt2xt*ptmin, pt2xt*ptmax);
  //c5->SetLogx();
  c5->Update();

}

Any hints on how to do that ?

Thanks in advance.

PS: ROOT 3.03/08 binaries on RedHat 7.1

david

-- 
 David d'Enterria                     PostDoctoral Research Scientist
 Nevis Labs                  http://www.nevis.columbia.edu/~denterria
 Columbia University, NY          mailto:denterria@nevis.columbia.edu
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 PHENIX Group (Bldg 510C)                        tel: +1 631 344 7053
 Brookhaven National Lab, Upton, NY 11973        fax: +1 631 344 3253
 http://www.phenix.bnl.gov/~enterria          mailto:denterri@bnl.gov
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