EMG

Note: this is old, naive code from a school project that I haven't touched in years. Using an object-oriented approach would have been a lot better. The signal processing bits are sound so use those for inspiration, but I discourage use of anything else here. It would be better to make your own processing scripts that you can understand and maintain yourself. I will not make any changes to this code, but you can ask questions about the signal processing aspects.

MATLAB functions and scripts for processing electromyography (EMG) signals.
Originally written for data from a CleveMed BioRadio comparing the tricep and deltoid during dumbbell press and perfect pushup, so some things (such as the process script) are specific to that, but most things will work for any EMG application.

Data Structures

EMG Structs

These scripts make use of structs to store and pass EMG data between functions. An EMG struct has the following elements:

Element	Meaning
`signal`	A list of the EMG samples
`time`	A list of time values corresponding to the samples, starting from 0
`l`	the length (number of samples) of the signal
`starts`	A list of the indexes of 'start' event markers
`stops`	A list of the indexes of 'stop' event markers
`n`	The number of pairs of 'start' and 'stop' event markers
`fs`	The sampling frequency in Hz

4-dimensional Array

The process script stores data in four-dimensional arrays with the first index corresponding to subject number, the second corresponding to exercise, the third corresponding to rep number, and the fourth corresponding to muscle number; i.e. movingrms(subject, exercise, rep, muscle). To get all of a certain index (e.g. all reps for a specific subject, exercise, and muscle) use a colon (:) in place of the index (e.g. array(subject, exercise, :, muscle)).

Signal Processing Functions

importemg

imports emg data from a csv file with the following columns:
deltoid, tricep, start events, stop events

For example:

deltoid,            tricep,             Start,  End,
-0.035858154296875, 0.444793701171875,  0,      0,
0,                  0.428009033203125,  0,      0,
-0.018310546875,    0.516510009765625,  0,      0,
...

Usage: [delt, tri] = importemg(filename, fs); where filename is the name of the file from which the data is to be imported and fs is the sampling frequency.

delt and tri are EMG structs

timebasis

Creates a list of time values starting from zero given a list of samples and the sampling frequency.

Usage: t = timebasis(signal, fs);
Where signal is the signal for which the time basis is to be created and fs is the sampling frequency in Hz. t is a list of time values corresponding to the samples in signal.

filteremg

Butterworth band-pass filters an EMG struct with a passband of 20-400 Hz unless cutoff frequencies are specified.
Usage:
filtered = filteremg(unfiltered); or
filtered = filteremg(unfiltered,fl,fh);
where fl is the low cutoff, and fh is the high cutoff of the passband in Hz.

deMainsEMG

Notch-filters an EMG struct at 60 Hz to remove interference from electrical systems.

Usage: filtered = deMainsEMG(unfiltered);

crop

Extracts a portion of an EMG signal using the start and stop endpoints.
Usage: exerpt = exerpt(emg, n);
Where n specifies which pair of start/stop event markers to use. For example, excerpt(emg, 3); returns the signal between the third 'start' event marker, and the third 'stop' event marker. Problems may occur if the event markers don't line up, for example if there's an extra 'start' at the beginning of the data.

movingRMS

Calculates the root mean square (RMS) of every n samples of an EMG signal Usage: RMS = movingRMS(emg, n);
where RMS and emg are both emg structs, and n is the number of samples to take in each RMS calculation.

process

Process is a script that uses the above functions to automatically import, process, and store all the EMG data for the project. It produces 4-D arrays of EMG structs containing the filtered EMG data, and the moving RMS with a 20-sample window. It also produces a 4-D array of the total RMS values.

Plotting Functions

plotemg

Creates a plot of an EMG signal including 'start' and 'stop' event markers.
Usage: plotemg(emg); where emg is an EMG struct. The signal is blue, 'start' events are green, and 'stop' events are red.

colorplotemg

Same as plotemg but allows specification of a color and line style for the signal.
Usage: plotemg(emg,color); where emg is an EMG struct and color is a string specifying color and line style (e.g. 'r-' for a red, solid line.

compareplot

Plots the signals from both exercises and both muscles for a specified subject and rep numbers.
Usage: compareplot(array, subject, drep, prep); where array is the 4-D array from which to get the data, subject is the subject number to use, drep is the rep to use for the first exercise (dumbbell press) and prep is the rep number to use for the second exercise (perfect pushup).

spectrumemg

Plots the spectrum of an EMG signal.
Usage: spectrumemg(emg); where emg is an EMG struct.

robbystk/emg

EMG

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