count_zeros.cpp

void count_zeros()
{
	// Now we can use the new and improved RDataFrame interface
	auto rdf = ROOT::RDataFrame("library_raw", "library.root");

	auto columns = rdf.GetColumnNames();
	auto empty_lst = std::map<std::string, size_t>();

	ProgressDisplay disp(*rdf.Count()*columns.size());

	size_t finished = 0;
	for(auto column : columns) {
		size_t empty_count = 0;
		rdf.Foreach([&](std::string s) {
			empty_count += (s == "");

			finished += 1;
			if(finished%100000 == 0)
				disp.update(finished);
		}, {column});
		empty_lst[column] = empty_count;
	}
	std::cout << "\n";

	for(auto [column, count] : empty_lst)
		std::cout << "Column " << column << ", have " << count << " empty entries" << std::endl;
}