A "ringdown" experiment records the amplitude of a resonator as it decays under the influence of the damping in the system, without any external input. Ringdown.m analyzes a data set from a resonator ringdown measurement and determines the resonator frequency and Q using different methods. An FFT is used to estimate the resonance frequency, and an exponential fit to the signal envelope is used to determine the Q. Finally, a minimum-search fit to the data set is performed to provide a second estimate of both values.