nanmedian.hpp

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#pragma once
 
#include <cmath>
#include <vector>
 
#include "NumCpp/Core/DtypeInfo.hpp"
#include "NumCpp/Core/Internal/StaticAsserts.hpp"
#include "NumCpp/Core/Internal/StlAlgorithms.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<dtype> nanmedian(const NdArray<dtype>& inArray, Axis inAxis = Axis::NONE)
    {
        STATIC_ASSERT_FLOAT(dtype);
 
        switch (inAxis)
        {
            case Axis::NONE:
            {
                std::vector<dtype> values;
                for (auto value : inArray)
                {
                    if (!std::isnan(value))
                    {
                        values.push_back(value);
                    }
                }
 
                const uint32 middle = static_cast<uint32>(values.size()) / 2;
                stl_algorithms::nth_element(values.begin(), values.begin() + middle, values.end());
                NdArray<dtype> returnArray = { values[middle] };
 
                return returnArray;
            }
            case Axis::COL:
            {
                const Shape    inShape = inArray.shape();
                NdArray<dtype> returnArray(1, inShape.rows);
                for (uint32 row = 0; row < inShape.rows; ++row)
                {
                    std::vector<dtype> values;
                    for (uint32 col = 0; col < inShape.cols; ++col)
                    {
                        if (!std::isnan(inArray(row, col)))
                        {
                            values.push_back(inArray(row, col));
                        }
                    }
 
                    const uint32 middle = static_cast<uint32>(values.size()) / 2;
                    stl_algorithms::nth_element(values.begin(), values.begin() + middle, values.end());
                    returnArray(0, row) = values[middle];
                }
 
                return returnArray;
            }
            case Axis::ROW:
            {
                return nanmedian(inArray.transpose(), Axis::COL);
            }
            default:
            {
                THROW_INVALID_ARGUMENT_ERROR("Unimplemented axis type.");
                return {}; // get rid of compiler warning
            }
        }
    }
} // namespace nc