Programmer Guide/Command Reference/EVAL/fft: Difference between revisions
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Fast fourier transform. | |||
---- | |||
;Usage 1:<code>fft(<var>x</var>)</code> | |||
:;<var>x</var>: 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 <code>[[./npow2|npow2(nrow( | |||
// (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===== | ||
Revision as of 11:19, 12 April 2011
Fast fourier transform.
- 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(
// (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)
