IFFT Inverse discrete Fourier transform.
    IFFT(X) is the inverse discrete Fourier transform of X.
 
    IFFT(X,N) is the N-point inverse transform.
 
    IFFT(X,[],DIM) or IFFT(X,N,DIM) is the inverse discrete Fourier
    transform of X across the dimension DIM.
 
    See also FFT, FFT2, IFFT2, FFTN, IFFTN, FFTSHIFT.