fftshift1 Perform a shift of the vector X, for use with the 'fft1' and 'ifft1' functions, in order the move the frequency 0 to the center of the vector or matrix. fftshift1 (X) fftshift1 (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. Perform a shift of the vector X, for use with the 'fft1' and 'ifft1' functions, in order the move the frequency 0 to the center of the vector or matrix. If X is a vector of N elements corresponding to N time samples spaced by dt, then 'fftshift1 (fft1 (X))' corresponds to frequencies f = [ -(ceil((N-1)/2):-1:1)*df 0 (1:floor((N-1)/2))*df ] where df = 1 / dt. If X is a matrix, the same holds for rows and columns. If X is an array, then the same holds along each dimension. The optional DIM argument can be used to limit the dimension along