ifftshift1 Undo the action of the 'fftshift1' function. ifftshift1 (X) ifftshift1 (X, DIM) X: It is a vector of N elements corresponding to time samples DIM: The optional DIM argument can be used to limit the dimension along which the permutation occurs This is an Octave function. Undo the action of the 'fftshift1' function. For even length X, 'fftshift1' is its own inverse, but odd lengths differ slightly.