doc/v624/basic_8C.html

#include "Riostream.h"

void basic() {

// read file $ROOTSYS/tutorials/tree/basic.dat

// this file has 3 columns of float data

   TString dir = gROOT->GetTutorialDir();

   dir.Append("/tree/");

   dir.ReplaceAll("/./","/");

   ifstream in;

   in.open(Form("%sbasic.dat",dir.Data()));


   Float_t x,y,z;

   Int_t nlines = 0;

   auto f = TFile::Open("basic.root","RECREATE");

   TH1F h1("h1","x distribution",100,-4,4);

   TNtuple ntuple("ntuple","data from ascii file","x:y:z");


   while (1) {

      in >> x >> y >> z;

      if (!in.good()) break;

      if (nlines < 5) printf("x=%8f, y=%8f, z=%8f\n",x,y,z);

      h1.Fill(x);

      ntuple.Fill(x,y,z);

      nlines++;

   }

   printf(" found %d points\n",nlines);


   in.close();


   f->Write();

}

f
#define f(i)
Definition RSha256.hxx:104

Riostream.h

Int_t
int Int_t
Definition RtypesCore.h:45

Float_t
float Float_t
Definition RtypesCore.h:57

gROOT
#define gROOT
Definition TROOT.h:406

Form
char * Form(const char *fmt,...)

TFile::Open
static TFile * Open(const char *name, Option_t *option="", const char *ftitle="", Int_t compress=ROOT::RCompressionSetting::EDefaults::kUseCompiledDefault, Int_t netopt=0)
Create / open a file.
Definition TFile.cxx:3997

TH1F
1-D histogram with a float per channel (see TH1 documentation)}
Definition TH1.h:575

TH1::Fill
virtual Int_t Fill(Double_t x)
Increment bin with abscissa X by 1.
Definition TH1.cxx:3350

TNtuple
A simple TTree restricted to a list of float variables only.
Definition TNtuple.h:28

TString
Basic string class.
Definition TString.h:136

TString::Data
const char * Data() const
Definition TString.h:369

TString::ReplaceAll
TString & ReplaceAll(const TString &s1, const TString &s2)
Definition TString.h:692

TString::Append
TString & Append(const char *cs)
Definition TString.h:564

y
Double_t y[n]
Definition legend1.C:17

x
Double_t x[n]
Definition legend1.C:17

h1
TH1F * h1
Definition legend1.C:5