I have such dataset
DT=structure(list(date = c("01.01.2021", "01.01.2021", "01.01.2021",
"01.01.2021", "01.01.2021", "01.01.2021", "01.01.2021", "01.01.2021",
"01.01.2021", "01.01.2021", "01.01.2021", "01.02.2021", "01.02.2021",
"01.02.2021", "01.02.2021", "01.02.2021", "01.02.2021", "01.02.2021",
"01.02.2021", "01.02.2021"), sales_count = c(10L, 4L, 8L, 6L,
4L, 4L, 4L, 3L, 1L, 5L, 2L, 10L, 5L, 9L, 2L, 8L, 5L, 6L, 8L,
3L)), class = "data.frame", row.names = c(NA, -20L))
it looks something like this
date sales_count
1 01.01.2021 10
2 01.01.2021 4
3 01.01.2021 8
4 01.01.2021 6
How can I remake the dataset so that it has exactly this input format
sales_count date_time date week_num weekday
1: 1 2016-05-02 00:00:00 2016-05-02 1 Monday
2: 10 2016-05-02 00:00:00 2016-05-02 1 Monday
3: 14 2016-05-02 00:00:00 2016-05-02 1 Monday
4: 15 2016-05-02 00:00:00 2016-05-02 1 Monday
5: 20 2016-05-02 00:00:00 2016-05-02 1 Monday