struct TData
{
  long long fCount;
  int       fSYear;
  int       fEYear;
};

static std::string fname_csv  = "ticket2.txt";
static std::string fname1_root = "ticket1.root";
static std::string fname2_root = "ticket2.root";
static std::string tname = "STB";

//______________________________________________________________________________________
void MakeDataFrame(
ROOT::RDF::RNode tdf_csv)
{ 
  auto calcColumns = [](const std::string &x)
  {
    static TPRegexp rl("(\\d{1,2})-Jahreskarte (\\d{4})");

    TData d;
    d.fCount   = 0;
    d.fSYear   = 0;
    d.fEYear   = -1;

    if (x.find("Jahreskarte") != std::string::npos)
    {
      const TObjArray *subStrL = rl.MatchS(x);
      if (subStrL->GetLast()+1 == 3)
      {
        const int length = ((TObjString *)subStrL->At(1))->GetString().Atoi();
        d.fSYear = ((TObjString *)subStrL->At(2))->GetString().Atoi();
        d.fEYear = d.fSYear+length-1;
      }
      else
      {
        Error("MakeDataFrame","Invalid data entry: %s",x.c_str());
      }
      delete subStrL;
    }

    return d;
  };

  // Insert a few columns
  auto tdf = tdf_csv.Define("data",calcColumns,{"fTicket"})
                    .Define("fSYear",  [](TData &data){return data.fSYear;},  {"data"})
                    .Define("fEYear",  [](TData &data){return data.fEYear;},  {"data"});
  tdf.Count();

  std::cout << "Column names of tdf before Snapshot: ";
  std::vector<std::string> colNames = tdf.GetColumnNames();
  for (auto &&name: colNames) {std::cout << name <<" ";} std::cout <<std::endl;

  // Store just fCount
  tdf.Snapshot(tname,fname1_root,{"fCount"});
  // Store everyting, so fCount and data.fCount
  tdf.Snapshot(tname,fname2_root);
}

//______________________________________________________________________________________
void mytest()
{
  auto tdf_csv = ROOT::RDF::MakeCsvDataFrame(fname_csv);

  MakeDataFrame(tdf_csv);

  ROOT::RDataFrame tdf1(tname,fname1_root);
  ROOT::RDataFrame tdf2(tname,fname2_root);

  std::cout << "Column names of tdf after Snapshot: ";
  std::vector<std::string> colNames2 = tdf2.GetColumnNames();
  for (auto &&name: colNames2) {std::cout << name <<" ";} std::cout << std::endl;

  long long count_sum = 0;
  tdf1.Foreach([&count_sum](long long count){count_sum += count;},{"fCount"} );
  std::cout << "sum counts of Snapshot with {\"fCount\"}: " << count_sum << std::endl;
  count_sum = 0;
  tdf2.Foreach([&count_sum](long long count){count_sum += count;},{"fCount"} );
  std::cout << "sum counts of Snapshot of everything: " << count_sum << std::endl;
}