All three methods, Autocorrelation, Enright and DFT predict approximately 1.17 minute periods in islet Ca²⁺ oscillations.

<p>(A) 30 minutes of oscillatory data representing Ca²⁺ oscillations; (B) Autocorrelation periodogram generated with the Autocorrelation method. The plot shows 5 significant local maxima obtained at the significance level of 0.01; (C) Enright periodogram generated by the Enright method. The plot shows 1 significant and 4 non significant local maxima obtained at the significance level of 0.01; (D) Frequency spectrum generated with the DFT method. The plot shows 3 significant and 2 non significant oscillatory periods obtained at the significance level of 0.01. Closed circles represent significant periods. Open circles represent non significant periods. We selected a maximum of five oscillatory candidate periods in each method. The candidates were ordered by the value of its period in the Autocorrelation and Enright methods, and by power in the DFT method.