WFDB Applications Guide - PhysioNet
WFDB Applications Guide - PhysioNet
WFDB Applications Guide - PhysioNet
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FFT(1) <strong>WFDB</strong> <strong>Applications</strong> <strong>Guide</strong> FFT(1)<br />
BUGS<br />
-z Add a constant to each input sample, chosen such that the mean value of the entire series is zero.<br />
-Z Set the mean value of the inputs to zero as for -z, and detrend the series (set its mean first derivative<br />
to zero). This is equivalent to subtracting a best-fit (by least squares) line from the input data.<br />
Because of accumulated round-off errors, the command<br />
fft -p file2<br />
may not produce an exact copy of file1 in file2, even ifthe number of samples is an exact power of 2. Using<br />
rectangular form, as in the command<br />
fft -c file2<br />
produces smaller errors, and is slightly faster than using polar form as in the first example.<br />
SEE ALSO<br />
coherence(1), hrfft(1), lomb(1), memse(1)<br />
AUTHOR<br />
George B. Moody (george@mit.edu)<br />
SOURCE<br />
http://www.physionet.org/physiotools/wfdb/psd/fft.c<br />
26 8 August 2002 <strong>WFDB</strong> 10.2.7
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