#include <iostream>
#include <fstream>
#include <vector>
#include <string>
#include <TH1D.h>
using namespace std;

TH1D* setBinContent( const std::string& fileName, const unsigned int nValues )
{
  ifstream infile( fileName.c_str(), std::ios::in );
  // if ( !infile.is_open() || infile.bad() ) 
  //     {
  //       std::cout << "Could not open input file at : " << fileName
  // 		<< std::endl;
  //       return 0;
  //     }

  std::vector<double> x( nValues );
  std::vector<double> y( nValues );

  // read file.
  // assume 1 columns
  for ( unsigned int i = 0; i != nValues; ++i )
    {
      infile >> y[i];
    }

  const unsigned int nbins = nValues;
  const double xMin = 0.;
  const double xMax = 10.;

  TH1D * h = new TH1D( "h", "Mon histo", nbins, xMin, xMax );
  for ( unsigned int i = 0; i != y.size(); ++i )
    {
      // assume each slot of the x vector corresponds to 1 bin
      // of the TH1D
      h->SetBinContent( i+1, y[i] );
    }

  infile.close();
  return h;
}

void histo2()
{
  TH1D* h=setBinContent("x.data",30);
}