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 y with ncol(x) columns and L+2 rows, where each column y[*,j] contains the complex spectrum of the column (channel) x[*,i]. The transformation length L is set to npow2(nrow(x)).

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Usage 2

fft(x, n {, ytype, poffset, prange, aref})

x

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

n

desired length of analysis window;

• If n < nrow(x), the analysis window length L is set to nrow(x), otherwise L is set to n.
• If the analysis window length L is a power of 2 (L=2^M), the fft algorithm is used, otherwise the dft is used.
• If L is greater than nrow(x), zero padding is applied to the signal.

ytype

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

See also

ifft, dft, dct, cepstrum, lpc, , complex arithmetic

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