Repeat the daily electricity example, but instead of using a quadratic function of temperature, use a piecewise linear function with the “knot” around 20 degrees Celsius (use predictors Temperature & Temp2). How can you optimize the choice of knot?
The data can be created as follows.
vic_elec_daily <- vic_elec |>
filter(year(Time) == 2014) |>
index_by(Date = date(Time)) |>
summarise(
Demand = sum(Demand)/1e3,
Temperature = max(Temperature),
Holiday = any(Holiday)
) |>
mutate(
Temp2 = I(pmax(Temperature-20,0)),
Day_Type = case_when(
Holiday ~ "Holiday",
wday(Date) %in% 2:6 ~ "Weekday",
TRUE ~ "Weekend"
)
)