Please, someone help me to understand this code.

I'm a beginner in MATLAB and i have to understand this code as it's important for my project. I request you guys to please help me to understand this code.

ec=xlsread('sumit_ecg.xlsx','B3:B1000003');
figure;
plot(ec);

j=1;
for i=2:length(ec)-1;
    if ec(i-1)< ec(i) && ec(i+1)<ec(i);
        ecgy1(j)=ec(i);
        ecgx1(j)=i;
        j=j+1;
    end
end

figure;plot(ec); hold on;
plot(ecgx1,ecgy1,'*');

j=j+1;
for i=1:length(ecgy1);
    if ecgy1(i)>=2;
        ecgy2(j)=ecgy1(i);
        ecgx2(j)=ecgx1(i);
        j=j+1;
    end
end

figure;plot(ec); hold on;
plot(ecgx2,ecgy2,'*');

Answer 1

[Image Analyst]

It would be easier if you'd attach your workbook, but it looks like it's doing some kind of peak detection where if an element is more than the prior one and subsequent one (so it's a local max), it logs/records the value of that local maximum.

Then it plots it and records where the peaks have a value of more than 2 and then plots those.

[Mohan Dubey]

Yaa, i have attached.

[Mohan Dubey]

Yaa, it's basically a R-peak detection of an ECG. Initially i guess, it detects all the peaks above certain value and then it detects R-peak from that. But, i am not able to understand the flow of this program.

[Image Analyst]

if ec(i-1)< ec(i) && ec(i+1)<ec(i);

basically sees if the i'th element is more than the elements on either side of it.

j is a counter so that the ecgx1 and ecgy1 only have the peak values and none of the values in between.

        ecgy1(j)=ec(i);
        ecgx1(j)=i;

The first line records the y value of the j'th peak. The second line records the index that the j'th peak occurred at.

[Mohan Dubey]

Thanks a lot. I get it.