Bulk RDF with functor class

array_column_ugly_first_version.cpp

#include <ROOT/RDataFrame.hxx>
#include <ROOT/RVec.hxx>
#include <iostream>

using ROOT::RVecF;
using ROOT::RVecU;

struct ToolAdapter {
  Tool tool;

  ToolAdapter() : tool(...) {}

  void operator()(const ROOT::RDF::Experimental::REventMask &eventMask,
                  ROOT::RVec<RVecF> &results, const ROOT::RVec<RVecF> &Muon_pts) {

    const auto size = eventMask.Size();
    for (std::size_t i = 0u; i < size; ++i) {
      if (eventMask[i]) {
        const auto sz = xs[i].size();
        tool.setcolumn("Muon_pt", Muon_pts[i].data(), Muon_pts[i].size());
        // ...
        results[i].resize(sz);
        tool.setoutput("...", results[i].data(), results[i].size();
        too.compute();
    }
  }
};

int main() {
  ROOT::RDataFrame df(10);
  auto m = df.Define("arr", [] { return RVecF{1.f,2.f,3.f}; })
             .Define("arrSquared", BulkSquare{}, {"arr"})
             .Mean<RVecF>("arrSquared")
             .GetValue();
  std::cout << "mean entry*entry: " << m << '\n';
}

scalar_column.cpp

#include <ROOT/RDataFrame.hxx>
#include <ROOT/RVec.hxx>
#include <iostream>

using ROOT::RVecF;
using ROOT::RVecU;

struct BulkSquare {
  void operator()(const ROOT::RDF::Experimental::REventMask &eventMask,
                  RVecF &results, const RVecF &xs) {
    const auto size = eventMask.Size();
    for (std::size_t i = 0u; i < size; ++i)
      if (eventMask[i])
        results[i] = xs[i] * xs[i];
  }
};

int main() {
  ROOT::RDataFrame df(10);
  auto m = df.Define("x", [](ULong64_t entry) { return float(entry); },
                     {"rdfentry_"})
               .Define("x2", BulkSquare{}, {"x"})
               .Mean<float>("x2")
               .GetValue();
  std::cout << "mean entry*entry: " << m << '\n';
}