Calculate relative values from peaks
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Hi I'd like to know how to calculate relative values from one or several peaks. If I use an EMG signal, I need to know, peak value and previus concentric contration and next eccentric contracction as shows the image Can anybody help me? Thanks!
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Star Strider
2016-5-20
No image.
I doubt you can tell a concentric contraction from an eccentric contraction from the EMG alone. (I’ve not worked with EMGs in a while, and don’t know your experimental setup, so I would need your data to confirm this.)
To upload the image, use the brown-framed green landscape picture icon. Remember to complete both the ‘Choose file’ and ‘Insert image’ steps.
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Star Strider
2016-5-20
The easiest way to define your peaks and troughs of your signal is to use the Signal Processing Toolbox findpeaks function. Use it on your original signal to find the peaks, then use it in a separate call on the negative of your signal to define the troughs.
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Star Strider
2016-6-7
You will get different results if your calls to findpeaks are different. You have to experiment to get the result you want.
It may be worthwhile for you to do a fft of your data to define the valid data and noise frequencies, then design a digital filter for your original data in that plot to eliminate some of the noise. Then do your findpeaks call on the filtered data.
There are several ways to design filters. My procedure is here: How to design a lowpass filter for ocean wave data in Matlab? You will have to decide whether you want a low-pass or band-pass filter, then experiment with the filter passband to get the result you want.
The problem is that your signal has so much noise that finding the peaks you want to use to define the concentric and eccentric contractions are going to be difficult without filtering it first. Give the filter idea a go and see if that improves your ability to identify the information you want.
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