Frequent Items Sketch C++ Example

#include <iostream>
#include <fstream>

#include <frequent_items_sketch.hpp>

//simplified file operations and no error handling for clarity
int main(int argc, char **argv) {
  typedef datasketches::frequent_items_sketch<std::string> frequent_strings_sketch;

  // this section generates two sketches and serializes them into files
  {
    frequent_strings_sketch sketch1(64);
    sketch1.update("a");
    sketch1.update("a");
    sketch1.update("b");
    sketch1.update("c");
    sketch1.update("a");
    sketch1.update("d");
    sketch1.update("a");
    std::ofstream os1("freq_str_sketch1.bin");
    sketch1.serialize(os1);

    frequent_strings_sketch sketch2(64);
    sketch2.update("e");
    sketch2.update("a");
    sketch2.update("f");
    sketch2.update("f");
    sketch2.update("f");
    sketch2.update("g");
    sketch2.update("a");
    sketch2.update("f");
    std::ofstream os2("freq_str_sketch2.bin");
    sketch2.serialize(os2);
  }

  // this section deserializes the sketches, produces a union and prints the result
  {
    std::ifstream is1("freq_str_sketch1.bin");
    frequent_strings_sketch sketch1 = frequent_strings_sketch::deserialize(is1);

    std::ifstream is2("freq_str_sketch2.bin");
    frequent_strings_sketch sketch2 = frequent_strings_sketch::deserialize(is2);

    // we could merge sketch2 into sketch1 or the other way around
    // this is an example of using a new sketch as a union and keeping the original sketches intact
    frequent_strings_sketch u(64);
    u.merge(sketch1);
    u.merge(sketch2);

    auto items = u.get_frequent_items(datasketches::NO_FALSE_POSITIVES);
    std::cout << "Frequent strings: " << items.size() << std::endl;
    std::cout << "Str\tEst\tLB\tUB" << std::endl;
    for (auto row: items) {
      std::cout << row.get_item() << "\t" << row.get_estimate() << "\t"
        << row.get_lower_bound() << "\t" << row.get_upper_bound() << std::endl;
    }
  }

  return 0;
}

Output:
Frequent strings: 7
Str	Est	LB	UB
a	6	6	6
f	4	4	4
c	1	1	1
d	1	1	1
e	1	1	1
b	1	1	1
g	1	1	1