vander.hpp

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#pragma once
 
#include <cmath>
#include <utility>
 
#include "NumCpp/Core/Enums.hpp"
#include "NumCpp/Core/Internal/StaticAsserts.hpp"
#include "NumCpp/Core/Internal/StdComplexOperators.hpp"
#include "NumCpp/Functions/fliplr.hpp"
#include "NumCpp/NdArray.hpp"
#include "NumCpp/Utils/powerf.hpp"
 
namespace nc
{
    //============================================================================
    // Method Description:
    template<typename dtype>
    auto vander(const NdArray<dtype>& x, uint32 n, Increasing increasing = Increasing::YES)
    {
        STATIC_ASSERT_ARITHMETIC_OR_COMPLEX(dtype);
 
        NdArray<decltype(std::pow(std::declval<dtype>(), uint32{ 0 }))> result(x.size(), n);
        for (uint32 row = 0; row < x.size(); ++row)
        {
            for (uint32 col = 0; col < n; ++col)
            {
                result(row, col) = std::pow(x[row], col);
            }
        }
 
        if (increasing == Increasing::NO)
        {
            return fliplr(result);
        }
 
        return result;
    }
 
    //============================================================================
    // Method Description:
    template<typename dtype>
    auto vander(const NdArray<dtype>& x, Increasing increasing = Increasing::YES)
    {
        return vander(x, x.size(), increasing);
    }
} // namespace nc