fft(var,length)

Calculates a raw Fast Fourier Transform (FFT) with no data windowing or concern about aliasing. You specify an input variable and a length which must be a constant power of 2. The input variable must not have any invalid points. This special transform requires a list of up to five output variables (that correspond to the frequency, real, imaginary, magnitude, and phase values), as described in “Transforms With Multiple Outputs”.