when using find peaks i get all the litlle peaks under 0.3 is there a way to detect only the 5 peaks? (without manually setting the threshold to be 0.3)
MATLAB: Looking for a better way to detect peaks
beatsecgfindpeaksheartheartbeatMATLABpeaksthreshold
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First, the time base is in seconds, not milliseconds. You can verify that by measuring the single R-R interval (0.85 s to my calphers).
The record is a Lead II rhythm strip. Normal sinus rhythm, rate 71 bpm. Both complete QRS complexes are 0.2 seconds (upper limit of the normal QRS is 0.12 seconds) with prominent S-waves. The QT segment is 0.38 seconds, approaching the upper limit of normal (0.4 s). The PR interval is 0.13 (normal 0.2 s). The T amplitude appears to be high. No pathological Q-waves or ST-T segment abnormalities are seen. The U-wave is prominent.
IMPRESSION: Abnormal EKG with short PR interval, intraventricular conduction delay characterised by pathologically prolonged QRS complexes, normal QT, elevated T-wave, and prominent U-wave consistent with hyperkalaemia, hypocalcaemia or drug effect. Suggest clinical correlation.
— Star Strider, M.D., Diplomate, American Board of Internal Medicine
It’s easiest to use the subscripts rather than the times to get the valleys. Also, there appears to be a bug in findpeaks such that supplying the sampling frequency does not produce the correct times for the peak locations. An easy workaround is to provide a time vector instead and use that.
See if this does what you want:
D = load('Krispy Scripts example.mat');datain=D.datain;fs=4e4;t = linspace(0, 1, length(datain))'/fs; % Time Vector
[pks,locs,w,p]=findpeaks(datain,t,'NPeaks',4);inverted=max(datain)-datain;pksmean=mean(pks);[valleys,locsvalley,wvalley,pvalley]=findpeaks(inverted,'NPeaks',4,'WidthReference','halfheight');valleysmean=mean(valleys);peakvalleyratio=pksmean/valleysmean;halfwidthaveragevalleys=mean(wvalley);valleys_actual = datain(locsvalley);valleys_time = t(locsvalley);figure(1)plot(t, datain)hold onplot(locs, pks, '^r', 'MarkerFaceColor','r')plot(valleys_time, valleys_actual, 'vr', 'MarkerFaceColor','r')hold offgridThe Plot —
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