WFDB Applications Guide - PhysioNet

HRFFT(1) WFDB Applications Guide HRFFT(1)
NAME
hrfft, hrlomb, hrmem − calculate and plot heart rate power spectra
hrplot − plot heart rate time series
SYNOPSIS
hrfft [ options ... ]
hrlomb [ options ... ]
hrmem [ options ... ]
hrplot [ options ... ]
DESCRIPTION
The first three of these UNIX shell scripts are intended to illustrate the use of fft(1), lomb(1), and
memse(1) by producing heart rate power spectra using the fast Fourier transform, the Lomb periodogram,
and the maximum entropy (all poles) method (also known as autoregressive, orAR, power spectral density
estimation). All four programs derive heart rate time series from beat annotation files. hrfft and hrmem
use tach(1) to obtain a uniformly resampled heart rate time series from the annotation file, which is then
used as input to fft or memse, and the spectrum thereby obtained is then plotted. hrlomb and hrplot use
ihr(1) to obtain an irregularly sampled heart rate time series. hrplot plots this time series directly, and
hrlomb uses it as input to lomb, and then plots the spectrum.
All four programs accept the same options:
-a annotator
Read annotations from the specified annotator (default: the value of the environment variable
ANNOTATOR, ifset).
-f time Begin at the specified time within the annotation file (default: the value of the environment variable
START, ifset, or the beginning of the file otherwise).
-l axes Log-transform the specified axes (default: use linear axes). The axes can be specified as x, y, or
xy.
-p plot-utility
Use the specified plot-utility to generate the output (default: the value of the environment variable
PLOT, ifset, or plt(1), if it exists, or plot2d(1) otherwise).
-r record
Produce a heart rate power spectrum for the specified record (default: the value of the environment
variable RECORD, ifset).
-t time Stop at the specified time within the annotation file (default: the value of the environment variable
END, ifset, or the end of the file otherwise).
-T device
Produce output on the specified device (default: the screen). The device must be among those supported
by the plot-utility (see above).
If annotator or record are not specified using environment variables or command-line options, these programs
obtain values from the user interactively.
Although hrfft, hrlomb, and hrmem all produce power spectra, the units of power differ among them.
Absolute comparisons can be made only between spectra produced using the same method, from time
series of the same length.
Note that these shell scripts can be run under MS-DOS using a suitable set of UNIX-like utilities, such as
the MKS Toolkit or the GNUish MS-DOS utilities, and under MS-Windows using the free Cygwin package.
ENVIRONMENT
In addition to the variables ANNOTATOR, END, PLOT, RECORD, and START, itmay be necessary to
set WFDB (see setwfdb(1)).
32 16 June 2003 WFDB 10.3.8