using namespace ROOT::RDF;

auto fileNameUrl = "http://root.cern/files/tutorials/df014_CsvDataSource_MuRun2010B.csv";
auto fileName = "df015_CsvDataSource_MuRun2010B.csv";
if(gSystem->AccessPathName(fileName))
   TFile::Cp(fileNameUrl, fileName);

auto csv_rdf = FromCSV(fileName);

std::string px1Name = "px1";
auto px1 = csv_rdf.Take<double>(px1Name);
std::string py1Name = "py1";
auto py1 = csv_rdf.Take<double>(py1Name);

auto df = MakeLazyDataFrame(std::make_pair(px1Name, px1), std::make_pair(py1Name, py1));

auto ptFormula = [](double px, double py) { return sqrt(px * px + py * py); };
auto pt_h = df.Define("pt", ptFormula, {"px1", "py1"})
              .Histo1D<double>({"pt", "Muon p_{T};p_{T} [GeV/c];", 128, 0, 128}, "pt");

auto can = new TCanvas();
can->SetLogy();
pt_h->DrawCopy();

return 0;

gROOT->GetListOfCanvases()->Draw()