find slope sign change of emg signal

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Ali Asghar
Ali Asghar 2019-8-16
回答： Star Strider 2019-8-18
dear
i want to find slope sign change of emg signal.
how i do this?
Thank you

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回答（2 个）

KSSV
KSSV 2019-8-16
If (t,x) is your time and signal.
dt = diff(t) ;
dx = diff(x) ;
slope = dx./dt ;
slope_sign = sign(slop) ;
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Ali Asghar
Ali Asghar 2019-8-18
dear
my data signal is 30000x4
time is 1x30000
its show error : Matrix dimensions must agree.

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Star Strider
Star Strider 2019-8-18
Use the gradient function to produce results that are the same sizes as your data, not diff.
If ‘EMG’ is your (30000x4) signal matrix, the derivative (‘dEMG’) is:
[~,dEMG] = gradient(EMG);
Note that taking the derivative of a a ‘real world’ signal will significantly amplify the noise. It would be best for you to use a lowpass filter on your EMG signal matrix first, to eliminate high-frequency noise. If you have R2018a or later, use the lowpass function (or bandpass if you also want to eliminate d-c offset and low-frequency baseline drift). Otherwise, efficient filters are not difficult to design and implement in MATLAB.

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