void plot()
{
  int day,hour,minute,second;  
  float time;
  float n[4];
  int i,nlines = 0;
 
  FILE *fp;
  fp=fopen("fq.txt","r"); 

  TFile *f=new TFile("plot.root","recreate");
  TTree *tree=new TTree("tree","");
  tree->Branch("time",&time,"time/F"); 
  tree->Branch("n",&n[0],"n[4]/F");

  while(!feof(fp))
    {      
      fscanf(fp,"%2d%2d%2d%2d ",&day,&hour,&minute,&second);
      for(i=0;i<4;i++)
          fscanf(fp,"%f",&n[i]);
      if(feof(fp))  break;      
      time=minute*60.0+second*1.0;
      tree->Fill();
      nlines++;
    }
  printf("found %d points \n",nlines);

  tree->Draw("n[0]:time","","l");
  fclose(fp);
  tree->Write();
  f->Write();  
}