fft21 Calculates the two-dimensional discrete Fourier transform of A using a Fast Fourier Transform algorithm. fft2 (A, m, n) fft2 (A) A: input matrix m: number of rows of A to be used n: number of columns of A to be used This is an Octave function. It performs two-dimentional FFT on the matrix A. m and n may be used specify the number of rows and columns of A to use. If either of these is larger than the size of A, A is resized and padded with zeros. If A is a multi-dimensional matrix, each two-dimensional sub-matrix of A is treated separately.