highpass {biosignalEMG} | R Documentation |
Highpass filter an EMG signal
Description
Highpass filter an EMG signal to remove signal artifacts and baseline noise contamination.
Usage
highpass(data, channel, cutoff = 50, n = 5, data.name)
Arguments
data |
an ‘emg’ object. |
channel |
in case of multi-channel data, |
cutoff |
cutoff frequency in Hertz for the highpass filter. See ‘Details’ for recommended values. |
n |
filter order for the highpass filter. |
data.name |
a string specifying the name of the variable which will appears on the plots. If empty or not provided is taken from the object given as |
Details
This procedure performs a highpass filtering to the EMG signal in order to remove signal artifacts and baseline noise contamination (such as the DC-bias).
There are various recommendations for the value of the cutoff frequency, for example 5Hz (Merletti, 1999) and 10-20Hz (Freriks et.al., 1999).
Value
An ‘emg’ object which contains the filtered EMG.
Note
This procedure only uses a butterworth type filter of order n
. In order to apply a different type of filter, please see the documentation of the ‘signal’ package.
Author(s)
J.A. Guerrero jaguerrero@correo.uaa.mx
References
Merletti R. (1999) Standards for Reporting EMG data. Journal of Electromyography and Kinesiology 9(1), III-IV http://www.isek-online.org/standards_emg.html
Freriks B., Stegeman D.F. and Hermens H.J. (1999) European Recommendations Standards for Surface Electromyography for Surface Electromyography, results of the SENIAM project. ISBN: 90-75452-14-4.
See Also
dcbiasremoval
, whitening
, lowpass
Examples
# Load a data.frame with EMG data
data(emg95306000)
# Coerce a data.frame into an 'emg' object
x <- as.emg(emg95306000, samplingrate = 1000, units = "mV")
# Filter the fourth channel in x
y <- highpass(x, cutoff = 100)
# change graphical parameters to show multiple plots
op <- par(mfcol = c(2, 2))
# Compute the rectified signals to see the effect of the filter
x_rect <- rectification(x)
y_rect <- rectification(y)
# plot the original channel, the filtered channel and the corresponding
# rectified signals
plot(x, channel = 1, main = "Original channel")
plot(y, main = "Highpass filtered channel")
plot(x_rect, main = "Rectified channel")
plot(y_rect, main = "Rectified highpass filtered channel")
# reset graphical parameters
par(op)