Finding Peak and Trough

Hello all,
I need to find the Peak and Trough for all the points in the attached graph and the data point used for plotting it. How do i find it. (Beginner pls excuse)

When you say peak and trough, do you just mean the co-ordinates of points on the graph? I'd use the following formula in the two rows next to the data, first just insert a row at the top and make cell A1 = 0:

In col B:

=AND(A2>A1,A2>A3)

In col C:
=AND(A2>A1,A2>A3)

THen just drag down. 'TRUE' in col B means it's found a peak, and 'TRUE' in C means a trough.

Let me know if it works!

Thanks for the suggestion , But am getting only one peak value but I would need to find out all the Peak and Trough and as shown in graph i have attached and i need to find the average of the peak and trough to get a polynomial curve... and the result from it...

Looks like a harmonic function, probably some kind of step-like instead of a sinewave; there's drift in the amplitude and frequency over time (looks like amplitude is increasing and frequency is decreasing), as well as a trend downards that may be linear but I guess might be logrithmic. Well, it might have some kind of second or third order behavior as a sinusoid rather than actually being a modified square wave.

Anyway, I doubt it's exactly a polynomial.

I feel like figuring out what kind of equation is governing this behavior is too fuzzy for a computer. Once you've got the formulation you can drive the coefficients down with least squares + solver, but the human needs to figure out what's going on here.

The above suggestion should return all local peaks and troughs.