df037_TTreeEventMatching.C File Reference

Detailed Description

This example shows processing of a TTree-based dataset with horizontal concatenations (friends) and event matching (based on TTreeIndex). In case the current event being processed does not match one (or more) of the friend datasets, one can use the FilterAvailable and DefaultValueFor functionalities to act upon the situation.

#include <TChain.h>
#include <TFile.h>
#include <TTree.h>
#include <TTreeIndex.h>
 
#include <ROOT/RDataFrame.hxx>
 
#include <iostream>
#include <numeric>
 
// A helper class to create the dataset for the tutorial below.
struct Dataset {
 
   constexpr static auto fMainFile{"df037_TTreeEventMatching_C_main.root"};
   constexpr static auto fAuxFile1{"df037_TTreeEventMatching_C_aux_1.root"};
   constexpr static auto fAuxFile2{"df037_TTreeEventMatching_C_aux_2.root"};
   constexpr static auto fMainTreeName{"events"};
   constexpr static auto fAuxTreeName1{"auxdata_1"};
   constexpr static auto fAuxTreeName2{"auxdata_2"};
 
   Dataset()
   {
      {
         TFile f(fMainFile, "RECREATE");
         TTree mainTree(fMainTreeName, fMainTreeName);
         int idx;
         int x;
         mainTree.Branch("idx", &idx, "idx/I");
         mainTree.Branch("x", &x, "x/I");
 
         idx = 1;
         x = 1;
         mainTree.Fill();
         idx = 2;
         x = 2;
         mainTree.Fill();
         idx = 3;
         x = 3;
         mainTree.Fill();
 
         mainTree.Write();
      }
      {
         // The first auxiliary file has matching indices 1 and 2, but not 3
         TFile f(fAuxFile1, "RECREATE");
         TTree auxTree(fAuxTreeName1, fAuxTreeName1);
         int y;
         int idx;
         auxTree.Branch("idx", &idx, "idx/I");
         auxTree.Branch("y", &y, "y/I");
 
         idx = 1;
         y = 4;
         auxTree.Fill();
         idx = 2;
         y = 5;
         auxTree.Fill();
 
         auxTree.Write();
      }
      {
         // The second auxiliary file has matching indices 1 and 3, but not 2
         TFile f(fAuxFile2, "RECREATE");
         TTree auxTree(fAuxTreeName2, fAuxTreeName2);
         int z;
         int idx;
         auxTree.Branch("idx", &idx, "idx/I");
         auxTree.Branch("z", &z, "z/I");
 
         idx = 1;
         z = 6;
         auxTree.Fill();
         idx = 3;
         z = 7;
         auxTree.Fill();
 
         auxTree.Write();
      }
   }
 
   ~Dataset()
   {
      std::remove(fMainFile);
      std::remove(fAuxFile1);
      std::remove(fAuxFile2);
   }
};
 
void df037_TTreeEventMatching()
{
   // Create the dataset: one main TTree and two auxiliary. The 'idx' branch
   // is used as the index to match events between the trees.
   // - The main tree has 3 entries, with 'idx' values (1, 2, 3).
   // - The first auxiliary tree has 2 entries, with 'idx' values (1, 2).
   // - The second auxiliary tree has 2 entries, with 'idx' values (1, 3).
   // The two auxiliary trees are concatenated horizontally with the main one.
   Dataset dataset{};
   TChain mainChain{dataset.fMainTreeName};
   mainChain.Add(dataset.fMainFile);
 
   TChain auxChain1(dataset.fAuxTreeName1);
   auxChain1.Add(dataset.fAuxFile1);
   auxChain1.BuildIndex("idx");
 
   TChain auxChain2(dataset.fAuxTreeName2);
   auxChain2.Add(dataset.fAuxFile2);
   auxChain2.BuildIndex("idx");
 
   mainChain.AddFriend(&auxChain1);
   mainChain.AddFriend(&auxChain2);
 
   // Create an RDataFrame to process the input dataset. The DefaultValueFor and
   // FilterAvailable functionalities can be used to decide what to do for
   // the events that do not match entirely according to the index column 'idx'
   ROOT::RDataFrame df{mainChain};
 
   const std::string auxTree1ColIdx = std::string(dataset.fAuxTreeName1) + ".idx";
   const std::string auxTree1ColY = std::string(dataset.fAuxTreeName1) + ".y";
   const std::string auxTree2ColIdx = std::string(dataset.fAuxTreeName2) + ".idx";
   const std::string auxTree2ColZ = std::string(dataset.fAuxTreeName2) + ".z";
 
   constexpr static auto defaultValue = std::numeric_limits<int>::min();
 
   // Example 1: provide default values for all columns in case there was no
   // match
   auto display1 = df.DefaultValueFor(auxTree1ColIdx, defaultValue)
                      .DefaultValueFor(auxTree1ColY, defaultValue)
                      .DefaultValueFor(auxTree2ColIdx, defaultValue)
                      .DefaultValueFor(auxTree2ColZ, defaultValue)
                      .Display<int, int, int, int, int, int>(
                         {"idx", auxTree1ColIdx, auxTree2ColIdx, "x", auxTree1ColY, auxTree2ColZ});
 
   // Example 2: skip the entire entry when there was no match for a column
   // in the first auxiliary tree, but keep the entries when there is no match
   // in the second auxiliary tree and provide a default value for those
   auto display2 = df.DefaultValueFor(auxTree2ColIdx, defaultValue)
                      .DefaultValueFor(auxTree2ColZ, defaultValue)
                      .FilterAvailable(auxTree1ColY)
                      .Display<int, int, int, int, int, int>(
                         {"idx", auxTree1ColIdx, auxTree2ColIdx, "x", auxTree1ColY, auxTree2ColZ});
 
   // Example 3: Keep entries from the main tree for which there is no
   // corresponding match in entries of the first auxiliary tree
   auto display3 = df.FilterMissing(auxTree1ColIdx).Display<int, int>({"idx", "x"});
 
   std::cout << "Example 1: provide default values for all columns\n";
   display1->Print();
   std::cout << "Example 2: skip the entry only when the first auxiliary tree does not match\n";
   display2->Print();
   std::cout << "Example 3: keep entries from the main tree for which there is no match in the auxiliary tree\n";
   display3->Print();
}

Example 1: provide default values for all columns
+-----+-----+---------------+---------------+---+-------------+-------------+
| Row | idx | auxdata_1.idx | auxdata_2.idx | x | auxdata_1.y | auxdata_2.z | 
+-----+-----+---------------+---------------+---+-------------+-------------+
| 0   | 1   | 1             | 1             | 1 | 4           | 6           | 
+-----+-----+---------------+---------------+---+-------------+-------------+
| 1   | 2   | 2             | -2147483648   | 2 | 5           | -2147483648 | 
+-----+-----+---------------+---------------+---+-------------+-------------+
| 2   | 3   | -2147483648   | 3             | 3 | -2147483648 | 7           | 
+-----+-----+---------------+---------------+---+-------------+-------------+
Example 2: skip the entry only when the first auxiliary tree does not match
+-----+-----+---------------+---------------+---+-------------+-------------+
| Row | idx | auxdata_1.idx | auxdata_2.idx | x | auxdata_1.y | auxdata_2.z | 
+-----+-----+---------------+---------------+---+-------------+-------------+
| 0   | 1   | 1             | 1             | 1 | 4           | 6           | 
+-----+-----+---------------+---------------+---+-------------+-------------+
| 1   | 2   | 2             | -2147483648   | 2 | 5           | -2147483648 | 
+-----+-----+---------------+---------------+---+-------------+-------------+
Example 3: keep entries from the main tree for which there is no match in the auxiliary tree
+-----+-----+---+
| Row | idx | x | 
+-----+-----+---+
| 2   | 3   | 3 | 
+-----+-----+---+

Date

September 2024

Author

Vincenzo Eduardo Padulano (CERN)

Definition in file df037_TTreeEventMatching.C.