Fast Fourier Transform
x An array of real or complex numbers.
y An array of complex numbers.

If the input is a one-dimensional array, the output of fft is the Fast Fourier Transform of the input. Prior to the computation of the transform, the input is padded with sufficient number of zeros so that the size of the padded array is a power of 2 .

If the input is a two-dimensional array, the output is a matrix with the same number of columns as in the input, with each column of y computed from the corresponding column of x in the manner described above.

>>title("Time Series")