Does an in-place Fourier transform of the current spectrum. This is a
discrete transform, and does not depend on the spectrum having
channels. Assumes that the original spectrum is real-symmetric about
the first channel, so that the resulting transform is real. With this
assumption the inverse transform and forward transform are identical, so
that this command can be applied repeatedly to move between real (spectral)
and transform (autocorrelation) space.
Examples:
>> fourier-transform<CR>
..
