How do I find a specific point in my plot?

So I have a series of ECG data plots and I need to find a specific point before each peak. I am stuck as to how to acomplish this.

Thanks!

[Cris LaPierre]

Have your tried searching the forum for questions about qrs detection?

[Julian Citino]

I didn't realise that was an option, thanks for the heads up

Answer 1

[Cris LaPierre]

Of course, the point you are probably looking for is the p wave. There are posts about that, too.