A concordance method for analyzing categorical time series. An applicationfor the search of periodicities

A simple method for searching for periods in biological series is proposed. Because it is based on an auto-comparison of the observations within a ser ies we call it the concordance method. It requires few theoritical assumpti ons. In fact, even the ever present stationarity condition is not used. The method is compared with competing methods based on the khi-square periodog ram. It is shown that the concordance method is much better for analyzing m ultimodal and noisy series. Rhythms presenting simultaneously circadian and ultradian components can also be analyzed with this method.