WIF - Combinators - Introduce majority combinator

Author: plnyrich

include/wif/combinators/majorityCombinator.hpp

@@ -0,0 +1,35 @@
+/**
+ * @file
+ * @author Richard Plny <[email protected]>
+ * @brief Majority combinator interface
+ *
+ * SPDX-License-Identifier: BSD-3-Clause
+ */
+
+#pragma once
+
+#include "combinator.hpp"
+
+#include <algorithm>
+
+namespace WIF {
+
+/**
+ * @brief MajorityCombinator class
+ *
+ * Perform majority vote by finding the prevalent element
+ */
+class MajorityCombinator : public Combinator {
+public:
+	/**
+	 * @brief Combine multiple values into one by using majority
+	 * The result is the first prevailing element.
+	 *
+	 * @throw std::runtime_error if an empty vector is passed
+	 * @param valuesToCombine vector of doubles to combine
+	 * @return double majority value in the provided vector
+	 */
+	double combine(const std::vector<double>& valuesToCombine) override;
+};
+
+} // namespace WIF

src/wif/CMakeLists.txt

@@ -5,6 +5,7 @@ set(LIBWIF_SOURCES
 	classifiers/scikitMlClassifier.cpp
 	combinators/averageCombinator.cpp
 	combinators/binaryDSTCombinator.cpp
+	combinators/majorityCombinator.cpp
 	combinators/sumCombinator.cpp
 	filesystem/fileModificationChecker.cpp
 	ml/scikitMlWrapper.cpp

src/wif/combinators/majorityCombinator.cpp

@@ -0,0 +1,49 @@
+/**
+ * @file
+ * @author Richard Plny <[email protected]>
+ * @brief Majority combinator implementation
+ *
+ * SPDX-License-Identifier: BSD-3-Clause
+ */
+
+#include "wif/combinators/majorityCombinator.hpp"
+
+#include <numeric>
+#include <stdexcept>
+
+namespace WIF {
+
+static double findPrevalentElement(std::vector<double> values)
+{
+	std::sort(values.begin(), values.end());
+
+	unsigned maxCount = 1;
+	unsigned currentCount = 1;
+	double candidate = values[0];
+
+	for (unsigned index = 1; index < values.size(); ++index) {
+		if (values[index] == values[index - 1]) {
+			++currentCount;
+		} else {
+			currentCount = 1;
+		}
+
+		if (currentCount > maxCount) {
+			maxCount = currentCount;
+			candidate = values[index - 1];
+		}
+	}
+
+	return candidate;
+}
+
+double MajorityCombinator::combine(const std::vector<double>& valuesToCombine)
+{
+	if (valuesToCombine.empty()) {
+		throw std::runtime_error("Nothing to combine! The supplied vector is empty.");
+	}
+
+	return findPrevalentElement(valuesToCombine);
+}
+
+} // namespace WIF