Provides a strong initialization for linear growth by calculating the
growth and offset parameters that pass the function through the first and
last points in the time series.
Usage
linear_growth_init(df)
Arguments
df
Data frame with columns ds (date), y_scaled (scaled time series),
and t (scaled time).
Value
A vector (k, m) with the rate (k) and offset (m) of the linear
growth function.