public static ComplexNumber[] DFT(ComplexNumber[] complexNumbers)
{
int N = complexNumbers.Length;
ComplexNumber[] complexNumbers2 = new ComplexNumber[N];
for (int k = 0; k < N; k++)
{
complexNumbers2[k] = new ComplexNumber(0, 0);
for (int n = 0; n < N; n++)
{
ComplexNumber tmp = ComplexNumber.ConvertFromPolarToRectangular(1, -2 * Math.PI * n * k / N);
tmp *= complexNumbers[n];
complexNumbers2[k] += tmp;
}
}
return(complexNumbers2);
}
public static ComplexNumber[] DIF_FFT(ComplexNumber[] complexNumbers)
{
int N = complexNumbers.Length;
ComplexNumber[] complexNumbers2 = new ComplexNumber[N];
ComplexNumber[] x, X, y, Y;
if (N == 1)
{
complexNumbers2[0] = complexNumbers[0];
return(complexNumbers2);
}
int k;
y = new ComplexNumber[N / 2];
x = new ComplexNumber[N / 2];
for (k = 0; k < N / 2; k++)
{
y[k] = complexNumbers[2 * k];
x[k] = complexNumbers[2 * k + 1];
}
X = DIF_FFT(x);
Y = DIF_FFT(y);
for (k = 0; k < N / 2; k++)
{
complexNumbers2[k] = Y[k] + X[k];
complexNumbers2[k + N / 2] = Y[k] - X[k];
}
for (k = 0; k < N / 2; k++)
{
ComplexNumber tmp = ComplexNumber.ConvertFromPolarToRectangular(1, -2 * Math.PI * k / N);
complexNumbers2[k] *= tmp;
}
return(complexNumbers2);
}