A Fast Chi-squared Technique For Period Search of Irregularly Sampled Data

A new, computationally- and statistically-efficient algorithm, the Fast ${\chi }^2$ algorithm, can find a periodic signal with harmonic content in irregularly-sampled data with non-uniform errors. The algorithm calculates the minimized ${\chi }^2$ as a function of frequency at the desired number of harmonics, using Fast Fourier Transforms to provide $O(N\log N)$ performance. The code for a reference implementation is provided.