The basic reproduction number of COVID is better to be extracted from the piecewise method of the first 2 weeks of data due to the relatively high sensitivity to the noise at the beginning when case numbers are small. 2 weeks of data give pretty consistent results from state to state with R0 ~ 3. The piecewise method can be applied to the full data set but is time-consuming. Thus, with proper smoothing, the real-time method is better to pull out the Rt values over time for the middle and later stages.