What's the fastest way to approximate the period of data using Octave?

Question

I have a set of data that is periodic (but not sinusoidal). I have a set of time values in one vector and a set of amplitudes in a second vector. I\'d like to quickly approximat

Answer 1

Take a look at the auto correlation function.

From Wikipedia

Autocorrelation is the cross-correlation of a signal with itself. Informally, it is the similarity between observations as a function of the time separation between them. It is a mathematical tool for finding repeating patterns, such as the presence of a periodic signal which has been buried under noise, or identifying the missing fundamental frequency in a signal implied by its harmonic frequencies. It is often used in signal processing for analyzing functions or series of values, such as time domain signals.

Paul Bourke has a description of how to calculate the autocorrelation function effectively based on the fast fourier transform (link).