mfft
====

multi-dimensional fft



Calling Sequence
~~~~~~~~~~~~~~~~


::

    [xk]=mfft(x,flag,dim)




Arguments
~~~~~~~~~

:x `x(i,j,k,...)` input signal in the form of a row vector whose
  values are arranged so that the i index runs the quickest, followed by
  the j index, etc.
: :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`
:



Description
~~~~~~~~~~~

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]`