FFT  FFT (Inverse) Fast Fourier Transform Function


Usage
 
 Computes the Discrete Fourier Transform (DFT) of a vector using the
 Fast Fourier Transform technique.  The general syntax for its use is
 
   y = fft(x,n,d)
 
 where x is an n-dimensional array of numerical type.
 Integer types are promoted to the double type prior to 
 calculation of the DFT. The argument n is the length of the
 FFT, and d is the dimension along which to take the DFT.  If
 |n| is larger than the length of x along dimension d,
 then x is zero-padded (by appending zeros) prior to calculation
 of the DFT.  If n is smaller than the length of x  along
 the given dimension, then x is truncated (by removing elements
 at the end) to length n.  
 
 If d is omitted, then the DFT is taken along the first 
 non-singleton dimension of x.  If n is omitted, then
 the DFT length is chosen to match of the length of x along
 dimension d.  
 