A Higher Order Fit for the CA Covid-19 Data

 

  Fitting a fifth degree polynomial to the rate of change, dK/dt, gave an even better fit to the CA Covid-19 Data. The coefficients of the powers of K were,

The resulting fits were,

Unfortunately, the signs of the lower order terms did not permit an estimate of the SIR model parameters.

Supplemental (Oct 22): It's doubtful this fit would make a good predictor over the long term since it is subject to errors near the end.