df036_missingBranches.C File Reference

Detailed Description

This example shows how to process a dataset where entries might be incomplete due to one or more missing branches in one or more of the files in the dataset. It shows usage of the FilterAvailable and DefaultValueFor RDataFrame functionalities to act upon the missing entries.

#include <ROOT/RDataFrame.hxx>
#include <TChain.h>
#include <TFile.h>
#include <TTree.h>
 
#include <iostream>
#include <numeric>
 
// A helper class to create the dataset for the tutorial below.
struct Dataset {
 
   constexpr static std::array<const char *, 3> fFileNames{"df036_missingBranches_C_file_1.root",
                                                           "df036_missingBranches_C_file_2.root",
                                                           "df036_missingBranches_C_file_3.root"};
   constexpr static std::array<const char *, 3> fTreeNames{"tree_1", "tree_2", "tree_3"};
   constexpr static auto fTreeEntries{5};
 
   Dataset()
   {
      {
         TFile f(fFileNames[0], "RECREATE");
         TTree t(fTreeNames[0], fTreeNames[0]);
         int x{};
         int y{};
         t.Branch("x", &x, "x/I");
         t.Branch("y", &y, "y/I");
         for (int i = 1; i <= fTreeEntries; i++) {
            x = i;
            y = 2 * i;
            t.Fill();
         }
 
         t.Write();
      }
 
      {
         TFile f(fFileNames[1], "RECREATE");
         TTree t(fTreeNames[1], fTreeNames[1]);
         int y{};
         t.Branch("y", &y, "y/I");
         for (int i = 1; i <= fTreeEntries; i++) {
            y = 3 * i;
            t.Fill();
         }
 
         t.Write();
      }
 
      {
         TFile f(fFileNames[2], "RECREATE");
         TTree t(fTreeNames[2], fTreeNames[2]);
         int x{};
         t.Branch("x", &x, "x/I");
         for (int i = 1; i <= fTreeEntries; i++) {
            x = 4 * i;
            t.Fill();
         }
 
         t.Write();
      }
   }
 
   ~Dataset()
   {
      for (auto &&fileName : fFileNames)
         std::remove(fileName);
   }
};
 
void df036_missingBranches()
{
   // Create the example dataset. Three files are created with one TTree each.
   // The first contains branches (x, y), the second only branch y, the third
   // only branch x.
   Dataset trees{};
 
   // The TChain will process the three files, encountering a different missing
   // branch when switching to the next tree
   TChain c{};
   for (auto i = 0; i < trees.fFileNames.size(); i++) {
      const auto fullPath = std::string(trees.fFileNames[i]) + "?#" + trees.fTreeNames[i];
      c.Add(fullPath.c_str());
   }
 
   ROOT::RDataFrame df{c};
 
   constexpr static auto defaultValue = std::numeric_limits<int>::min();
 
   // Example 1: provide a default value for all missing branches
   auto display1 = df.DefaultValueFor("x", defaultValue)
                      .DefaultValueFor("y", defaultValue)
                      .Display<int, int>({"x", "y"}, /*nRows*/ 15);
 
   // Example 2: provide a default value for branch y, but skip events where
   // branch x is missing
   auto display2 =
      df.DefaultValueFor("y", defaultValue).FilterAvailable("x").Display<int, int>({"x", "y"}, /*nRows*/ 15);
 
   // Example 3: only keep events where branch y is missing and display values for branch x
   auto display3 = df.FilterMissing("y").Display<int>({"x"}, /*nRows*/ 15);
 
   std::cout << "Example 1: provide a default value for all missing branches\n";
   display1->Print();
 
   std::cout << "Example 2: provide a default value for branch y, but skip events where branch x is missing\n";
   display2->Print();
 
   std::cout << "Example 3: only keep events where branch y is missing and display values for branch x\n";
   display3->Print();
}

 
Example 1: provide a default value for all missing branches
+-----+-------------+-------------+
| Row | x           | y           | 
+-----+-------------+-------------+
| 0   | 1           | 2           | 
+-----+-------------+-------------+
| 1   | 2           | 4           | 
+-----+-------------+-------------+
| 2   | 3           | 6           | 
+-----+-------------+-------------+
| 3   | 4           | 8           | 
+-----+-------------+-------------+
| 4   | 5           | 10          | 
+-----+-------------+-------------+
| 5   | -2147483648 | 3           | 
+-----+-------------+-------------+
| 6   | -2147483648 | 6           | 
+-----+-------------+-------------+
| 7   | -2147483648 | 9           | 
+-----+-------------+-------------+
| 8   | -2147483648 | 12          | 
+-----+-------------+-------------+
| 9   | -2147483648 | 15          | 
+-----+-------------+-------------+
| 10  | 4           | -2147483648 | 
+-----+-------------+-------------+
| 11  | 8           | -2147483648 | 
+-----+-------------+-------------+
| 12  | 12          | -2147483648 | 
+-----+-------------+-------------+
| 13  | 16          | -2147483648 | 
+-----+-------------+-------------+
| 14  | 20          | -2147483648 | 
+-----+-------------+-------------+
Example 2: provide a default value for branch y, but skip events where branch x is missing
+-----+----+-------------+
| Row | x  | y           | 
+-----+----+-------------+
| 0   | 1  | 2           | 
+-----+----+-------------+
| 1   | 2  | 4           | 
+-----+----+-------------+
| 2   | 3  | 6           | 
+-----+----+-------------+
| 3   | 4  | 8           | 
+-----+----+-------------+
| 4   | 5  | 10          | 
+-----+----+-------------+
| 10  | 4  | -2147483648 | 
+-----+----+-------------+
| 11  | 8  | -2147483648 | 
+-----+----+-------------+
| 12  | 12 | -2147483648 | 
+-----+----+-------------+
| 13  | 16 | -2147483648 | 
+-----+----+-------------+
| 14  | 20 | -2147483648 | 
+-----+----+-------------+
Example 3: only keep events where branch y is missing and display values for branch x
+-----+----+
| Row | x  | 
+-----+----+
| 10  | 4  | 
+-----+----+
| 11  | 8  | 
+-----+----+
| 12  | 12 | 
+-----+----+
| 13  | 16 | 
+-----+----+
| 14  | 20 | 
+-----+----+

Date

September 2024

Author

Vincenzo Eduardo Padulano (CERN)

Definition in file df036_missingBranches.C.