average_calculator.h

[詳解]

 
 
// Copyright(c) 2023-2025 Design Engineering Laboratory, Saitama University
// Released under the MIT license
// https://opensource.org/licenses/mit-license.php
 
#ifndef DESIGNLAB_AVERAGE_CALCULATOR_H_
#define DESIGNLAB_AVERAGE_CALCULATOR_H_
 
#include <cmath>
#include <optional>
#include <vector>
 
namespace designlab {
 
template <typename T, typename = std::enable_if_t<std::is_arithmetic<T>::value>>
class AverageCalculator final {
 public:
  AverageCalculator()
      : data_(),
        sum_(std::nullopt),
        average_(std::nullopt),
        variance_(std::nullopt),
        standard_deviation_(std::nullopt) {}
 
  void AddData(const T& data, const bool do_calc = true) {
    data_.push_back(data);
 
    if (sum_.has_value()) {
      sum_ = sum_.value() + data;
    } else {
      sum_ = data;
    }
 
    if (do_calc) {
      Calculate();
    }
  }
 
  void Clear() {
    data_.clear();
    sum_ = std::nullopt;
    average_ = std::nullopt;
    variance_ = std::nullopt;
    standard_deviation_ = std::nullopt;
  }
 
  void Calculate() {
    // データが空の場合は,平均値,分散,標準偏差を nullopt にする.
    if (data_.empty()) {
      average_ = std::nullopt;
      variance_ = std::nullopt;
      standard_deviation_ = std::nullopt;
      return;
    }
 
    // 平均値を求める.
    average_ = sum_.value() / data_.size();
 
    // 分散を求める.
    T variance_sum = 0;
 
    for (const auto& data : data_) {
      variance_sum += (data - average_.value()) * (data - average_.value());
    }
    variance_ = variance_sum / data_.size();
 
    // 標準偏差を求める.
    standard_deviation_ = sqrt(variance_.value());
  }
 
  std::optional<T> GetAverage() const { return average_; }
 
  std::optional<T> GetVariance() const { return variance_; }
 
  std::optional<T> GetStandardDeviation() const { return standard_deviation_; }
 
  size_t GetDataNum() const { return data_.size(); }
 
  std::optional<T> GetSum() const { return sum_; }
 
 private:
  std::vector<T> data_;
  std::optional<T> sum_;
  std::optional<T> average_;
  std::optional<T> variance_;
  std::optional<T> standard_deviation_;
};
 
}  // namespace designlab
 
#endif  // DESIGNLAB_AVERAGE_CALCULATOR_H_