Zooming problem with TGraph

From: Marco Calviani <marco.calviani_at_gmail.com>
Date: Fri, 28 Apr 2006 17:45:38 +0200

Hi rooters,
  i'm trying to create a graph (with bar errors) using TGraphErrors, reading the data from an ASCII file. It succesfully creates the graph but when i try to zoom or on the X or on the Y axis, the lowest limit remains blocked on the minimum. How is it possible?

void leggi()
{
  TCanvas *c1= new TCanvas("c1","c1",200,10,700,500);    int nlines=0,n=0;
   FILE *file;
   file=fopen("xs.dat","r");
   if(file==NULL)
{

        cout << "Errore apertura file!" << endl;
     }

   char riga[10000];
   float energy_,xs_,xserr_;
   float energy[10000],xs[10000],xserr[10000];    while(fscanf(file,"\n%[^\n]",riga)>EOF)
{

        sscanf(riga, "%f %f %f", &energy_,&xs_,&xserr_);
        energy[n]=energy_;
        xs[n]=xs_;
        xserr[n]=xserr_;
        nlines++;
        n++;
     }

   fclose(file);
   cout << nlines << endl;

  TH2F *hpx = new TH2F("hpx","Sezione d'urto ^{245}Cm",nlines,0.01,5000000,1000,0.01,10000.);

   hpx->SetStats(kFALSE);
   hpx->Draw();
   hpx->GetXaxis()->CenterTitle();
   hpx->GetXaxis()->SetTitle("E_{n} (eV)");
   hpx->GetYaxis()->CenterTitle();
   hpx->GetYaxis()->SetTitle("#sigma (barn)");

   TGraphErrors *gr = new TGraphErrors(nlines,energy,xs,0,xserr);

   gPad->SetLogy(kTRUE);
   gPad->SetLogx(kTRUE);
   gPad->Modified();
   gPad->Update();
   gr->SetMarkerStyle(21);
   gr->SetMarkerSize(0.5);
   gr->SetMarkerColor(4);
   gr->Draw("LP");
   c1->SetGrid(kTRUE);

   c1->Modified();
   c1->Update();
}

Many thanks in advance,
MC Received on Fri Apr 28 2006 - 17:45:45 MEST