Programmer Guide/Command Reference/EVAL/fft

Fast fourier transform.

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Usage 1

fft(x)

x

signal vector or matrix; if x is a matrix a spectrum of each column is computed

Result

A matrix containing a complex spectrum for each column (channel) of the input signal x. The transformation length L is set to [[./npow2|npow2(nrow(x))]]

// (1) fft( X ) // function: // if X is a vector: compute the fft spectrum of X // if X is a matrix: compute the fft spectrum of each row of X // the fft length L is set to the next power of 2 of nrow(X) // if L is greater than nrow(X), zero padding is applied // result: // vector or matrix Y containing one complex spectrum per row; // nrow(Y) = L+2, ncol(Y) = ncol(X)

fft

fft(x)fft(x, n)

Calculate the FFT of the vector x. If the parameter n is given and n >= nrow(x), then n is used as the signal length. The next possible value of x^2 is used for the FFT length (if necessary, 0 samples are added to x). The result is a complex FFT spectrum with 2^(m-1)+1 complex values (2^m = FFT length)

See also

ifft, dft, dct, cepstrum, lpc

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