how do i find the P-R and Q-T interval and QRS duration from a ECG data?

hi, i want to get the interval of P-R and Q-T and the QRS duration from a data set tahts a ECG but also a graph that can display the ecg with the the peak, P wave and T wave with the P R Q T S being labelled. what i have currently is below

clc;

clear all;

close all;

load('Sample_1');

ecg=Orig_Sig;

samplingrate=360;

fresult=fft(ecg);

fresult(1 : round(length(fresult)*6/samplingrate))=0;

fresult(end - round(length(fresult)*6/samplingrate) : end)=0;

corrected=real(ifft(fresult));

c_ecg=corrected;

EKG=c_ecg;

Fs=360;

t=[0:size(EKG)-1/Fs];

[R2,TR] = findpeaks( EKG, t, 'MinPeakHeight', 50);

[QS,TQS] = findpeaks(-EKG, t, 'MinPeakHeight', 75);

plot(t, EKG)

hold on

plot(TR, R2, '^r')

plot(TQS(1:2:end), -QS(1:2:end), 'vg')

plot(TQS(2:2:end), -QS(2:2:end), 'vb')

hold off

grid

axis([0 2 ylim])

legend('EKG', 'R', 'Q', 'S')

this is what i hgave so far, its only creating a grpah that isnt working but the ecg data should be processed into a relatively smooth line.

i ahve also attached the ecg data below.

[Batara nababan]

Error in Untitled (line 5)

ecg = Orig_Sig;