Fourier coefficients

If the `COS&SIN` keyword is used, then the `FFT` function returns the actual Fourier coefficients.

Let the cosine coefficients be called 's and let the sine coefficients be called 's. is the mean value of the input data. As shown in the example below, these coefficients can be used for smoothing and interpolation. Suppose is the interpolation location, and `2N` is the number of original data points.

If the `COS&SIN` keyword is used, then the `FFT` function returns the actual Fourier coefficients. Let the cosine coefficients be called 's and the sine coefficients be called 's. is the mean value of the input data. As shown in the example below, these coefficients can be used for smooth interpolation. Suppose is the interpolation location, and `2N` is the number of original data points.

Fast Fourier transform
Discrete Fourier series