522446 v2 basic functions

2026 4 2
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更新时间：2026 4 2
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1.1 Functions:
  • Diff()
  • Trapz()
  • Cumtrapz()
Cumtrapz(1/Fs, sig.^2)
Cumtrapz(Y, dim)
- where Y = time dimension = 1 / frequency
  • Dim = amplitudes
Making time vector t = (0:length - 1) / Fs
1.3 Functions:
  • Snr()
  • (power) --> mean(x.^2)
  • SNR = 10*log10(power signal / power noise)
Signal = (index: index)
Noise = (index:index)
Powersignal = (mean(sig.^2))
Powernoise = mean(noise.^2)
1.4 Functions
  • Always use 4th order filter
  • Check cutoff freq by plotting
  • Rectify signal --> abs(sig)
  • Filter rectified signal --> butter() ---> filtfilt()
[b,a] = butter(4,4/(Fs/2), '[filter type]')
Env1 - filtfilt(b,a,abs(sig1))
Env2 = filtfilt(b,a,abs(sig2))
1.5 Functions
  • Downsample()
  • Interp1()
Downsample factor = Fs_original / Fs_downsample
Downsample(sig, downsample factor)
Interp1(x,y,t,'[interp method]')
Where x = downsample time vector (1/Fs)
Where y = signal downsampled
Where t = time vector with time values that don't have y value
2.2 Functions
  • Sig = sig-mean(sig)
  • Lowpass filt
OR
  • DC OFFSET = 0 Hz signal
  • Make cutoff (0.1 --> x)
  • Bandpass filt
Mean(diff(t)) = Fs
Fc = [0.1 100]/(Fs/2)
DC OFFSET REMOVAL
  • Sig = sig-mean(sig)
Noise removal (lowpass)
[b,a] = butter(4, 10/(Fs/2), 'low')
Sigfilt = filtfilt(b,a,sig)
2.3 Functions
  • iirnotch()
Wo = 60/(Fs/2)
Bw = 2/(Fs/2)
60 Hz for North America
Wo = noise freq
Bw = bandwidth
2.4 Functions
  • EMG, ECG, EEG
  • EMG: freqs up to 400-500 Hz
  • ECG/EEG: freqs up to 50 Hz
  • ECG: Large peak at 1-2 Hz (heartbeat)
  • EEG: no large peak at 1-2 Hz

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John D'Errico
John D'Errico about 3 hours 前
What is your question (concerning MATLAB) in this?

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Matthias
Matthias
2026-4-2，19:44

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John D'Errico
John D'Errico
2026-4-2，23:27

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