Peak phase determination for a tim-luc timecourse. The fluctuating luminescence data were collected from a series of isolated, cultured fly wings in 12-h:12-h LD cycles. (a) The enzyme-reported molecular timecourse for each of 15 specimens. The appearance of synchronous waves suggests that the several heads exhibited similarly phased clock-gene-expression rhythmicities. (b) Scatter plot of mean peak phase values (per day) for each specimen. The zero-hour phase corresponds to the times of lights on, so 12 of the 15 specimens gave average peak luminescence in a 2 hour window preceding lights-on. (c) Unit-circle representation of the head-rhythm phase data. The circle defines a polar coordinate plot with radians transformed to hours. The inner dotted circle is the unit one and the dotted lines cross at the origin. The magnitude of a mean vector in this plot describes the coherence of the various phases of the head samples. The phase points taken from each specimen are plotted around the circle just beyond the unit circumference. The mean vector extends from the origin in the direction of -0.3 hours and has a magnitude that nearly reaches 1, indicating strong phase coherence.. The coefficient is a z-score and was determined to be signifiant at p < 0.01 by Rayleigh's test (see text).