doc/hackathon/tree101__basic_8C.html

#include "Riostream.h"


void tree101_basic()

{

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

   // this file has 3 columns of float data

   TString dir = gROOT->GetTutorialDir();

   dir.Append("/io/tree/");

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

   ifstream in;

   in.open(TString::Format("%sbasic.dat", dir.Data()));


   Float_t x, y, z;

   Int_t nlines = 0;

   auto f = TFile::Open("tree101.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 = %+8.6f, y = %+8.6f, z = %+8.6f\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
Signed integer 4 bytes (int).
Definition RtypesCore.h:59

Float_t
float Float_t
Float 4 bytes (float).
Definition RtypesCore.h:71

gROOT
#define gROOT
Definition TROOT.h:417

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:3787

TH1F
1-D histogram with a float per channel (see TH1 documentation)
Definition TH1.h:878

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

TString
Basic string class.
Definition TString.h:138

TString::Data
const char * Data() const
Definition TString.h:384

TString::ReplaceAll
TString & ReplaceAll(const TString &s1, const TString &s2)
Definition TString.h:713

TString::Append
TString & Append(const char *cs)
Definition TString.h:581

TString::Format
static TString Format(const char *fmt,...)
Static method which formats a string using a printf style format descriptor and return a TString.
Definition TString.cxx:2385

ifstream
STL class.

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