Asked by Krish P
on 5 Jan 2013

Is there an easy way to find all local minima of an noisy ecg signal(ecg+baseline wander)with out using function? After that all local maxima are to be connected by a cubic spline curve as the upper envelope e1(t), similarly all local minima by a spline curve as the lower envelope e2(t).Next step is to find the mean of the two envelope ie

m1(t)= [e1(t)+e2(t)]/2.

PROGRAM UP TO GENERATION OF ECG NOISY SIGNAL

n=512; fs=n/.83; tp=.83*10; x1=ecg(512); t=0:1/fs:tp-1/fs; z=repmat(x1,1,10); subplot(231); plot(t,z); title('ecg signal'); xlabel('time'); ylabel('amplitude'); t2=0:1/512:10-(1/512); s1=.1*cos(2*pi*.5*t2); s2=.1*cos(2*pi*.4*t2); baseline=s1+s2; subplot(232); plot(t2,baseline); %BASELINE WANDER xlabel('time'); ylabel('amplitude'); y=z+baseline; % NOISY ECG disp(y); subplot(233); plot(t,y); % NOISY ECG

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Answer by Walter Roberson
on 5 Jan 2013

Edited by Walter Roberson
on 5 Jan 2013

Accepted answer

local_mins = find( signal(1:end-2) > signal(2:end-1) & signal(2:end-1) < signal(3:end) ); local_maxs = find( signal(1:end-2) < signal(2:end-1) & signal(2:end-1) > signal(3:end) ); e1 = spline( local_mins, signal(local_mins), 1:length(signal) ); e2 = spline( local_maxs, signal(local_maxs), 1:length(signal) ); m1 = (e1 + e2) / 2;

Krish P
on 5 Jan 2013

Thank you so much Sir.

saleema
on 6 Dec 2014

sir, i want a matlab codes for finding local maxima and local minima and after their envelop by using spline interpolation

Image Analyst
on 6 Dec 2014

Post a new question, and say if you have the Image Processing Toolbox (so you can use imdilate and imerode to get the local max and min).

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