nanmean.hpp

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#pragma once
 
#include <algorithm>
#include <cmath>
 
#include "NumCpp/Core/DtypeInfo.hpp"
#include "NumCpp/Core/Internal/StaticAsserts.hpp"
#include "NumCpp/Core/Shape.hpp"
#include "NumCpp/Core/Types.hpp"
#include "NumCpp/Functions/max.hpp"
#include "NumCpp/NdArray.hpp"
 
namespace nc
{
    //============================================================================
    // Method Description:
    template<typename dtype>
    NdArray<double> nanmean(const NdArray<dtype>& inArray, Axis inAxis = Axis::NONE)
    {
        STATIC_ASSERT_FLOAT(dtype);
 
        switch (inAxis)
        {
            case Axis::NONE:
            {
                auto sum = static_cast<double>(
                    std::accumulate(inArray.cbegin(),
                                    inArray.cend(),
                                    0.,
                                    [](dtype inValue1, dtype inValue2) -> dtype
                                    { return std::isnan(inValue2) ? inValue1 : inValue1 + inValue2; }));
 
                const auto numberNonNan =
                    static_cast<double>(std::accumulate(inArray.cbegin(),
                                                        inArray.cend(),
                                                        0.,
                                                        [](dtype inValue1, dtype inValue2) -> dtype
                                                        { return std::isnan(inValue2) ? inValue1 : inValue1 + 1; }));
 
                NdArray<double> returnArray = { sum /= numberNonNan };
 
                return returnArray;
            }
            case Axis::COL:
            {
                const Shape     inShape = inArray.shape();
                NdArray<double> returnArray(1, inShape.rows);
                for (uint32 row = 0; row < inShape.rows; ++row)
                {
                    auto sum = static_cast<double>(
                        std::accumulate(inArray.cbegin(row),
                                        inArray.cend(row),
                                        0.,
                                        [](dtype inValue1, dtype inValue2) -> dtype
                                        { return std::isnan(inValue2) ? inValue1 : inValue1 + inValue2; }));
 
                    auto numberNonNan = static_cast<double>(
                        std::accumulate(inArray.cbegin(row),
                                        inArray.cend(row),
                                        0.,
                                        [](dtype inValue1, dtype inValue2) -> dtype
                                        { return std::isnan(inValue2) ? inValue1 : inValue1 + 1; }));
 
                    returnArray(0, row) = sum / numberNonNan;
                }
 
                return returnArray;
            }
            case Axis::ROW:
            {
                return nanmean(inArray.transpose(), Axis::COL);
            }
            default:
            {
                THROW_INVALID_ARGUMENT_ERROR("Unimplemented axis type.");
                return {}; // get rid of compiler warning
            }
        }
    }
} // namespace nc