(date - 1L) %in% holidays_2013$date ~ "day before holiday", (date + 1L) %in% holidays_2013$date ~ "day after holiday",
I think you mixed up these two.
(date + 1L) %in% holidays_2013$date ~ "day before holiday",
(date - 1L) %in% holidays_2013$date ~ "day after holiday",
(α+βx)
should be $$\beta \log x$$
the more that pre-allocation will outperform appending.
Based on the output, it seems to me that appending outperform the pre-allocation. I run the code myself, got same results. However, another R notebook gave opposite results.