bincount.hpp

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#pragma once
 
#include <string>
 
#include "NumCpp/Core/Internal/Error.hpp"
#include "NumCpp/Core/Internal/StaticAsserts.hpp"
#include "NumCpp/Core/Internal/StlAlgorithms.hpp"
#include "NumCpp/Core/Types.hpp"
#include "NumCpp/NdArray.hpp"
 
namespace nc
{
    //============================================================================
    // Method Description:
    template<typename dtype>
    NdArray<dtype> bincount(const NdArray<dtype>& inArray, uint16 inMinLength = 1)
    {
        STATIC_ASSERT_INTEGER(dtype);
 
        dtype maxValue = inArray.max().item();
        if (maxValue < 0)
        {
            // no positive values so just return an empty array
            return NdArray<dtype>(0);
        }
 
        if (maxValue + 1 > DtypeInfo<dtype>::max())
        {
            THROW_INVALID_ARGUMENT_ERROR(
                "array values too large, will result in gigantic array that will take up alot of memory...");
        }
 
        const uint16   outArraySize = std::max(static_cast<uint16>(maxValue + 1), inMinLength);
        NdArray<dtype> clippedArray = inArray.clip(0, maxValue);
 
        NdArray<dtype> outArray(1, outArraySize);
        outArray.zeros();
        std::for_each(clippedArray.cbegin(),
                      clippedArray.cend(),
                      [&outArray](dtype value) noexcept -> void { ++outArray[value]; });
 
        return outArray;
    }
 
    //============================================================================
    // Method Description:
    template<typename dtype>
    NdArray<dtype> bincount(const NdArray<dtype>& inArray, const NdArray<dtype>& inWeights, uint16 inMinLength = 1)
    {
        STATIC_ASSERT_INTEGER(dtype);
 
        if (inArray.shape() != inWeights.shape())
        {
            THROW_INVALID_ARGUMENT_ERROR("weights array must be the same shape as the input array.");
        }
 
        dtype maxValue = inArray.max().item();
        if (maxValue < 0)
        {
            // no positive values so just return an empty array
            return NdArray<dtype>(0);
        }
 
        if (maxValue + 1 > DtypeInfo<dtype>::max())
        {
            THROW_INVALID_ARGUMENT_ERROR(
                "array values too large, will result in gigantic array that will take up alot of memory...");
        }
 
        const uint16   outArraySize = std::max(static_cast<uint16>(maxValue + 1), inMinLength);
        NdArray<dtype> clippedArray = inArray.clip(0, maxValue);
 
        NdArray<dtype> outArray(1, outArraySize);
        outArray.zeros();
        uint32 counter = 0;
        std::for_each(clippedArray.cbegin(),
                      clippedArray.cend(),
                      [&outArray, &inWeights, &counter](dtype value) noexcept -> void
                      { outArray[value] += inWeights[counter++]; });
 
        return outArray;
    }
} // namespace nc