C++ Program to Compute Discrete Fourier Transform Using Naive Approach

Code:

#include  iostream
#include  math.h

using namespace std;

#define PI 3.14159265

class DFT_Coefficient
{
    public:
        double real, img;
        DFT_Coefficient()
        {
            real = 0.0;
            img = 0.0;
        }
};
int main(int argc, char **argv)
{
    int N = 10;
    cout << "Discrete Fourier Transform using naive method\n";
    cout << "Enter the coefficient of simple linear function:\n";
    cout << "ax + by = c\n";
    double a, b, c;
    cin >> a >> b >> c;

    double function[N];
    for (int i = 0; i < N; i++)
    {
        function[i] = (((a * (double) i) + (b * (double) i)) - c);
        //System.out.print( "  "+function[i] + "  ");
    }

    cout << "Enter the max K value: ";
    int k;
    cin >> k;

    double cosine[N];
    double sine[N];

    for (int i = 0; i < N; i++)
    {
        cosine[i] = cos((2 * i * k * PI) / N);
        sine[i] = sin((2 * i * k * PI) / N);
    }

    DFT_Coefficient dft_val[k];
    cout << "The coefficients are: ";
    for (int j = 0; j < k; j++)
    {
        for (int i = 0; i < N; i++)
        {
            dft_val[j].real += function[i] * cosine[i];
            dft_val[j].img += function[i] * sine[i];
        }
        cout << "(" << dft_val[j].real << ") - " << "(" << dft_val[j].img << " i)\n";
    }
}


Output:

Discrete Fourier Transform using naive method
Enter the coefficient of simple linear function:
ax + by = c
1 2 3
Enter the max K value: 20
The coefficients are: 
(105) - (-1.03386e-005 i)
(105) - (-1.03386e-005 i)
(105) - (-1.03386e-005 i)
(105) - (-1.03386e-005 i)
(105) - (-1.03386e-005 i)
(105) - (-1.03386e-005 i)
(105) - (-1.03386e-005 i)
(105) - (-1.03386e-005 i)
(105) - (-1.03386e-005 i)
(105) - (-1.03386e-005 i)
(105) - (-1.03386e-005 i)
(105) - (-1.03386e-005 i)
(105) - (-1.03386e-005 i)
(105) - (-1.03386e-005 i)
(105) - (-1.03386e-005 i)
(105) - (-1.03386e-005 i)
(105) - (-1.03386e-005 i)
(105) - (-1.03386e-005 i)
(105) - (-1.03386e-005 i)
(105) - (-1.03386e-005 i)




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