Error in range, Inf/NaN propagated to the pad

[lm17n000032]

Hi ROOTers,

I wrote a code in order to plot Betfhe-Bloch function, it works but if i change range it doesn’t work, I don’t understand why. I post code and output.

#include<string>
#include<iostream>

Double_t bethe_bloch(Double_t *x, Double_t *par) 
{

  Double_t E=x[0];
  Double_t S; //MeV/cm
  Double_t phi;
  Double_t rap = par[1]/par[2];
  Double_t I= (9.76*par[4])+pow(58.8*par[4],0.19);
  
  //phi = ((par[2])/(2*E))*(log((4*par[1]*E/(par[2]-2*E))/(I + I*sqrt(par[2]/(par[2]-2*E))*rap)) - (2*E)/(par[2]));
 
  phi=(par[2]/(2*E))*log(((4*par[1]*E)/(par[2]-2*E))/(I+I*sqrt(par[2]/(par[2]-2*E))*rap)+2*E/par[2]);

  
  S = -par[0]*(par[4]/par[5])*par[6]*par[3]*phi;
  
  return S;
}
  
  void bethe()
 {

    TF1 *f1= new TF1("f1",bethe_bloch, 0,100,7);
    f1->FixParameter(0,0.30707);// D in (MeV*cm^2)/(mol)
    f1->FixParameter(1, 0.510998928); //mec2 in MeV
    f1->FixParameter(2,105);// Mc2 in MeV
    f1->FixParameter(3, 1); // z2 
    f1->FixParameter(4, 53); // Z
    f1->FixParameter(5, 139); // A
    f1->FixParameter(6, 2.266); //densità
    
    

    f1->GetXaxis()->SetTitle("E");
	f1->GetYaxis()->SetTitle("#frac{N_{S}}{cm}");
    f1->SetTitle("Curva teorica Bethe-Bloch");


    TCanvas *c1 = new TCanvas();

    f1->Draw();
    
    c1->SaveAs("bethe.pdf");
    

 }  

Warning in <TCanvas::ResizePad>: Inf/NaN propagated to the pad. Check drawn objects.
Warning in <TCanvas::ResizePad>: c1 height changed from 0 to 10

Info in <TCanvas::Print>: pdf file bethe.pdf has been created
root [1] Warning in <TCanvas::ResizePad>: Inf/NaN propagated to the pad. Check drawn objects.
Warning in <TCanvas::ResizePad>: c1 height changed from 0 to 10

Warning in <TCanvas::ResizePad>: Inf/NaN propagated to the pad. Check drawn objects.
Warning in <TCanvas::ResizePad>: c1 height changed from 0 to 10

---

_ROOT Version: 6.13/03
_Platform: Xubuntu 18.04
_Compiler: gcc 7.2.0

---

[Wile_E_Coyote]

You must make sure that the arguments of the standard “pow”, “log”, “sqrt” and your own functions are valid and do not generate floating-point errors:

  TF1 *f1 = new TF1("f1", bethe_bloch, 1.e-3, 50.0, 7); f1->SetNpx(1000);

[lm17n000032]

Thank you so much, now I understand the error.