onoff_bonato {biosignalEMG} | R Documentation |
Automatic detection algorithm to determine the times at which muscles “turn on” (activity periods) and “turn off” (silence periods) in an EMG signal.
onoff_bonato(data, channel, sigma_n, Pfa = 0.05, m = 5, r0 = 1, minL = 15, data.name)
data |
an ‘emg’ object. |
channel |
in case of multi-channel data, |
sigma_n |
standard deviation of the baseline noise (need to be estimated). |
Pfa |
false-alarm probability (see ‘Details’). |
m |
number of samples observed to perform the detection. |
r0 |
minimum number of samples out of |
minL |
minimum length allowed of the detected phases. |
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 |
This technique of detection consists of selecting a initial threshold (such that the probability of false alarm is Pfa
) and then observing m
successive samples: if
at least r0
out of the m
successive samples are above the threshold the presence of the signal is acknowledged.
A numeric vector with values 0 (silence) and 1 (activity).
The default values of m
and minL
where choosen for a sampling rate of 500Hz.
J.A. Guerrero jaguerrero@correo.uaa.mx
Bonato P., D'Alessio T. and Knaflitz M. (1998) A statistical method for the measurement of muscle activation intervals from surface myoelectric signal during gait. IEEE Transactions on Biomedical Engineering 45 (3), 287–299. ISSN 0018–9294.
# 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")
# change graphical parameters to show multiple plots
op <- par(mfrow = c(2, 1))
# Estimate 'sigma_n' from the last 200 samples (only baseline noise)
sigma_n <- sd(tail(x$values, 200))
# Detect the phases of activation in x
b <- onoff_bonato(x, sigma_n = sigma_n, m = 10, minL = 30)
# Plot 'x' and the detected phases
plot(x, main = "Sample EMG")
plot(b, type = "l", main = "Detected phases (Bonato's method)")
# reset graphical parameters
par(op)