r - 无法在 R 中设置天数和天名(日期始终为字符)

Question

要重现的样本数据

a=structure(list(date = c("01.01.2021", "02.01.2021", "03.01.2021", 
"04.01.2021", "05.01.2021", "06.01.2021", "07.01.2021", "08.01.2021", 
"09.01.2021", "10.01.2021", "11.01.2021", "12.01.2021", "13.01.2021", 
"14.01.2021", "15.01.2021", "16.01.2021", "17.01.2021", "18.01.2021", 
"19.01.2021", "20.01.2021"), 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))

为什么我加载数据时，日期是字符？我得到了错误。我的尝试

a$date = as.Date (a$date)lError in charToDate (x):character string is not in a standard unambiguous format

Error in charToDate (x):
   character string is not in a standard unambiguous format

我在 SO 中看到许多类似的帖子，但这些解决方案对我没有帮助。如何修复这个错误，那个日期是

date     : Date, format: "2021-01-20" ...

然后如何为每个日期分配日期名称和天数？例如，确实是我想要的输出

sales_count date    day_num weekday
8        2021-01-20   3 Wednesday

谢谢。

Answer 1

您可以使用以下解决方案:

library(dplyr)

a %>%
  mutate(date = as.Date(date, "%d.%m.%Y"), 
         weekday = weekdays(date))

         date sales_count   weekday
1  2021-01-01          10    Friday
2  2021-01-02           4  Saturday
3  2021-01-03           8    Sunday
4  2021-01-04           6    Monday
5  2021-01-05           4   Tuesday
6  2021-01-06           4 Wednesday
7  2021-01-07           4  Thursday
8  2021-01-08           3    Friday
9  2021-01-09           1  Saturday
10 2021-01-10           5    Sunday
11 2021-01-11           2    Monday
12 2021-01-12          10   Tuesday
13 2021-01-13           5 Wednesday
14 2021-01-14           9  Thursday
15 2021-01-15           2    Friday
16 2021-01-16           8  Saturday
17 2021-01-17           5    Sunday
18 2021-01-18           6    Monday
19 2021-01-19           8   Tuesday
20 2021-01-20           3 Wednesday

或者我们可以使用 lubridate 包。我们应该将等同于base::weekdays 的wday 函数的label 参数设置为TRUE，否则它返回从周日开始的工作日数:

library(lubridate)

a %>%
  mutate(date = dmy(date), 
         weekday = wday(date, label = TRUE))