  fft
  Builtin Function



      SSyynnooppssiiss
        Discrete Fourier Transform.

      SSyynnttaaxx
        fft ( _X )

        fft ( _X, _N )

      DDeessccrriippttiioonn
        Fft utilizes the FFTPACK subroutine CFFTF to compute a discrete
        forward Fourier transform of the input.

        If fft is used with a second argument, _N, then the matrix _X is
        either padded with zeros, or truncated till it is of length _N
        (if _X is a vector), or has row dimension _N (if it is a matrix).

        Subroutine CFFTF computes the forward complex discrete Fourier
        transform (the Fourier analysis). equivalently , CFFTF computes
        the Fourier coefficients of a complex periodic sequence.



                  for j=1,...,n

                     c(j)=the sum from k=1,...,n of

                           c(k)*exp(-i*(j-1)*(k-1)*2*pi/n)

                                 where i=sqrt(-1)





     The argument _X must be a matrix. If _X is a row, or column matrix
     then a vector fft is performed. If _X is a MxN matrix then the _N
     columns of _X are fft'ed.


     SSeeee AAllssoo
        ifft




















