best way to detect sinusoidal pattern

What is the best way to filter patterns that looks like a sine wave e.g the 1st one is selected and the last one is filtered out

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Answer 1

[John D'Errico]

Neither of these is truly sinusoidal. At best, you might say the first has an oscillatory behavior. Note that the first one has a strong semi-linear trend in it too. But sinusoidal? Not so. And if it is not actually sinusoidal, your question becomes a bit moot, as now one can only ask about the amplitude of semi-periodic behavior.

So if you wanted that, then you might consider an FFT. See what it can tell you about those patterns. For example, if you saw a strong amplitude at some frequency, what might it tell you?

Or perhaps the wavelet toolbox might be even more appropriate for your purposes.