multi-dimensional fft
[xk]=mfft(x,flag,dim)
: :flag (-1) FFT or (1) inverse FFT : :dim dimension vector which gives the number of values of x for
each of its indices
: :xk output of multidimensional fft in same format as for x :
FFT for a multi-dimensional signal
For example for a three dimensional vector which has three points along its first dimension, two points along its second dimension and three points along its third dimension the row vector is arranged as follows
x=[x(1,1,1),x(2,1,1),x(3,1,1),
x(1,2,1),x(2,2,1),x(3,2,1),
x(1,1,2),x(2,1,2),x(3,1,2),
x(1,2,2),x(2,2,2),x(3,2,2),
x(1,1,3),x(2,1,3),x(3,1,3),
x(1,2,3),x(2,2,3),x(3,2,3)]
and the dim vector is: dim=[3,2,3]