How to plot 3 seconds worth of ECG data from excel and perform a DFT to find the power spectrum

Hello, I have a code asking me to:

1. The file avf.csv contains 3 minutes of a noisy ECG signal. The first column of data is the time intervals a sample was taken, and the second column of data is the magnitude of the ECG in mV. Perform the following using the ECG data:
2. Plot 3 seconds worth of the ECG and label the plot appropriately.
3. Perform a DFT (with the DFT function) and create a separate plot of the power spectrum. Label the plot appropriately.

I think I have plotted the ECG wave for 3 seconds correctly but I am not sure that I have done the DFT function correctly to create a power spectrum. I also need to make my amplitude one sided and I am not sure how to do that. Can someone please verify my code and help me out with my errors.

I have also attached my file

here is my code:

Excel = csvread('avf.csv');
Fs = 1/(Excel(2,1)-Excel(1,1));
N = 3*Fs+1; %L
T = N/Fs;
t = (0:1:N-1)/Fs;
%x = avf(1:N, 1);
f = (0:1:N-1)*Fs/N;
y = avf(1:N, 2); %xt
plot(t,y)
xlabel('time(s)'); ylabel('amp'); title('Signal');

xt = y

fk = Fs*(0:(N-1))/N;
L = N + 24
xt = [y, zeros(N,24)];
Xk = fft(xt,N);
Ak = abs(Xk)/N;
%Y = fft(xt);
%P2 = abs(Y/N);
%P1 = P2(1:L/2+1);
%Pq(2:end-1) = 2*pi(2:end-1)
%Ak = 1/N*abs(Y);
Pk = Ak.^2

figure(2);
plot(fk,Pk);
title('DFT');
xlabel('Frequency(HZ)');
ylabel('Amplitude Spectrum');

Answer 1

[Harshita Gokavi]

Excel = csvread('avf.csv');

Fs = 1/(Excel(2,1)-Excel(1,1));

N = 3*Fs+1; %L

T = N/Fs;

t = (0:1:N-1)/Fs;

%x = avf(1:N, 1);

f = (0:1:N-1)*Fs/N;

y = avf(1:N, 2); %xt

plot(t,y)

xlabel('time(s)'); ylabel('amp'); title('Signal');

xt = y

fk = Fs*(0:(N-1))/N;

L = N + 24

xt = [y, zeros(N,24)];

Xk = fft(xt,N);

Ak = abs(Xk)/N;

%Y = fft(xt);

%P2 = abs(Y/N);

%P1 = P2(1:L/2+1);

%Pq(2:end-1) = 2*pi(2:end-1)

%Ak = 1/N*abs(Y);

Pk = Ak.^2

figure(2);

plot(fk,Pk);

title('DFT');

xlabel('Frequency(HZ)');

ylabel('Amplitude Spectrum');