missing_creator.cpp

void missing_creator()
{
	// Now we can use the new and improved RDataFrame interface
	auto rdf = ROOT::RDataFrame("library", "library.root");
	auto rdf_missing = rdf.Filter("creator != \"\" && publication_year != 0x7fffffff");
	std::map<std::string, int> books;
	rdf_missing.Foreach([&](std::string title, int year) {books[title] = year;}, {"title", "publication_year"});
	auto h1 = new TH1F("h1", "books with missing creator", 100, 1850, 2019);
	for(auto [title, year] : books)
		h1->Fill(year);
	h1->Draw();
}