Από το αρχείο βοήθειας του matlab: help fft FFT Discrete Fourier transform. FFT(X) is the discrete Fourier transform (DFT) of vector X. For matrices, the FFT operation is applied to each column. For N-D arrays, the FFT operation operates on the first non-singleton dimension. FFT(X,N) is the N-point FFT, padded with zeros if X has less than N points and truncated if it has more. FFT(X,[],DIM) or FFT(X,N,DIM) applies the FFT operation across the dimension DIM. For length N input vector x, the DFT is a length N vector X, with elements N X(k) = sum x(n)*exp(-j*2*pi*(k-1)*(n-1)/N), 1 <= k <= N. n=1 The inverse DFT (computed by IFFT) is given by N x(n) = (1/N) sum X(k)*exp( j*2*pi*(k-1)*(n-1)/N), 1 <= n <= N. k=1 See also fft2, fftn, fftshift, fftw, ifft, ifft2, ifftn. FFT2 Two-dimensional discrete Fourier Transform. FFT2(X) returns the two-dimensional Fourier transform of matrix X. If X is a vector, the result will have the same orientation. FFT2(X,MROWS,NCOLS) pads matrix X with zeros to size MROWS-by-NCOLS before transforming.