statistics.hpp

Go to the documentation of this file.

// Copyright (c) 2020-2025 Cody R. Drisko. All rights reserved.
// Licensed under the MIT License. See the LICENSE file in the project root for more information.
//
// Name: statistics.hpp
// Author: cdrisko
// Date: 02/03/2020-08:22:29
// Description: Common mathematical functions relating to statistics
 
#ifndef DRYCHEM_COMMON_UTILITIES_INCLUDE_COMMON_UTILS_MATH_STATISTICS_STATISTICS_HPP
#define DRYCHEM_COMMON_UTILITIES_INCLUDE_COMMON_UTILS_MATH_STATISTICS_STATISTICS_HPP
 
#include <cmath>
#include <cstddef>
#include <iterator>
#include <numeric>
#include <type_traits>
#include <utility>
 
namespace CppUtils::Math
{
    template<typename T, typename = std::enable_if_t<std::is_arithmetic_v<T>>>
    constexpr int findOrderOfMagnitude(T value) noexcept
    {
        return static_cast<int>(std::floor(std::log10(value)));
    }
 

    template<typename T, typename = std::enable_if_t<std::is_arithmetic_v<T>>>
    constexpr long double findAbsoluteError(T expectedValue, std::size_t significantFigures) noexcept
    {
        return std::pow(10, findOrderOfMagnitude(expectedValue) - (significantFigures - 1));
    }
 

    template<typename Iterator, typename T = typename std::iterator_traits<Iterator>::value_type,
             typename = std::enable_if_t<std::is_default_constructible_v<T>>>
    constexpr T calculateAverage(Iterator x_begin, Iterator x_end)
    {
        T init {};
        T result {std::accumulate(x_begin, x_end, init) / (x_end - x_begin)};
 
        return result;
    }
 

    template<typename Iterator, typename T = typename std::iterator_traits<Iterator>::value_type,
             typename = std::enable_if_t<std::is_default_constructible_v<T>>>
    constexpr decltype(auto) calculateVariance(Iterator x_begin, Iterator x_end)
    {
        using Txx = decltype(*x_begin * *x_begin);
 
        std::ptrdiff_t x_size {x_end - x_begin};
 
        T average {calculateAverage(x_begin, x_end)};
 
        Txx init {};
        Txx result = std::accumulate(x_begin, x_end, init,
            [&average](Txx res, T x) { return std::move(res) + ((x - average) * (x - average)); }) / (x_size - 1);
 
        return result;
    }
}   // namespace CppUtils::Math
 
#endif