How to measure ECG waves

How to measure the P,QRS, and T waves on this graph?

load load('EKG Traces (3x).mat')
dt_EKG2=detrend (EKG2)
plot(time2,dt_EKG2)

[Mathieu NOE]

hello

this topic seems to be recurrent on this forum - have a look at the others posts

like

How can I extract ST segment ,PR interval and QT interval from ECG signal?Plz help... - MATLAB Answers - MATLAB Central (mathworks.com)