将日期转换为年份和周数并返回

Question

我想将日期转换为年和周数的组合。稍后我想再次转换回日期。我不明白为什么无法在相同的原始日期返回，即使我尝试了所有不同的周开始数字：

library(dplyr)

df <- tidyr::expand_grid(
  date = as.Date(paste("2021 12 29"), "%Y %m %d") + 0:10,
  weekday = 0:6
)

df <- df %>%
  mutate(
    year = format(date, "%Y"),
    week = format(date, "%W"),
    newDate = as.Date(paste(year, week, weekday), format = "%Y %W %w")
  ) %>%
  tidyr::pivot_wider(
    id_cols = c("date"), names_from = "weekday", 
    values_from = "newDate"
  )

print(df)
# A tibble: 11 x 8
   date       `0`        `1`        `2`        `3`        `4`        `5`        `6`       
   <date>     <date>     <date>     <date>     <date>     <date>     <date>     <date>    
 1 2021-12-29 2021-12-26 2021-12-27 2021-12-28 2021-12-29 2021-12-30 2021-12-31 NA        
 2 2021-12-30 2021-12-26 2021-12-27 2021-12-28 2021-12-29 2021-12-30 2021-12-31 NA        
 3 2021-12-31 2021-12-26 2021-12-27 2021-12-28 2021-12-29 2021-12-30 2021-12-31 NA        
 4 2022-01-01 NA         NA         NA         NA         NA         NA         2022-01-01
 5 2022-01-02 NA         NA         NA         NA         NA         NA         2022-01-01
 6 2022-01-03 2022-01-02 2022-01-03 2022-01-04 2022-01-05 2022-01-06 2022-01-07 2022-01-08
 7 2022-01-04 2022-01-02 2022-01-03 2022-01-04 2022-01-05 2022-01-06 2022-01-07 2022-01-08
 8 2022-01-05 2022-01-02 2022-01-03 2022-01-04 2022-01-05 2022-01-06 2022-01-07 2022-01-08
 9 2022-01-06 2022-01-02 2022-01-03 2022-01-04 2022-01-05 2022-01-06 2022-01-07 2022-01-08
10 2022-01-07 2022-01-02 2022-01-03 2022-01-04 2022-01-05 2022-01-06 2022-01-07 2022-01-08
11 2022-01-08 2022-01-02 2022-01-03 2022-01-04 2022-01-05 2022-01-06 2022-01-07 2022-01-08

为什么没有不包含 NA 的列？

sessionInfo() 的输出：

R version 3.6.2 (2019-12-12)
Platform: x86_64-w64-mingw32/x64 (64-bit)
Running under: Windows 10 x64 (build 17763)

Matrix products: default

locale:
[1] LC_COLLATE=English_United Kingdom.1252  LC_CTYPE=English_United Kingdom.1252   
[3] LC_MONETARY=English_United Kingdom.1252 LC_NUMERIC=C                           
[5] LC_TIME=English_United Kingdom.1252

Answer 1

现在您将 newDate 设置为等于特定年份的特定月份，然后是 7 天范围内的范围。这就是为什么 newDate 目前是：

"2021-01-03" "2021-01-04" "2021-01-05" "2021-01-06" "2021-01-07" "2021-01-01" "2021-01-02" NA

要获得返回与最初相同日期的所需输出，您还必须存储日期并在创建 newDate 时引用它。简而言之，这样做：

date <- as.Date(paste("2021 01 03"), "%Y %m %d")
year <- format(date, "%Y")
week <- format(date, "%W")
day <- format(date, "%d")
newDate <- as.Date(paste(year, week, day), format = "%Y %W %w")

Answer 2

%G 和 %V 解决了我的问题：

library(dplyr)

df <- tidyr::expand_grid(
  date = as.Date(paste("2021 12 26"), "%Y %m %d") + 0:10,
  weekday = 0:6
)

df <- df %>%
  mutate(
    year = format(date, "%G"),
    week = format(date, "%V"),
    newDate = as.Date(paste(year, week, weekday), format = "%Y %W %w")
  ) %>%
  tidyr::pivot_wider(
    id_cols = c("date", "year", "week"), names_from = "weekday", 
    values_from = "newDate"
  )

print(df)
# A tibble: 11 x 10
   date       year  week  `0`        `1`        `2`        `3`        `4`        `5`       
   <date>     <chr> <chr> <date>     <date>     <date>     <date>     <date>     <date>    
 1 2021-12-26 2021  51    2021-12-19 2021-12-20 2021-12-21 2021-12-22 2021-12-23 2021-12-24
 2 2021-12-27 2021  52    2021-12-26 2021-12-27 2021-12-28 2021-12-29 2021-12-30 2021-12-31
 3 2021-12-28 2021  52    2021-12-26 2021-12-27 2021-12-28 2021-12-29 2021-12-30 2021-12-31
 4 2021-12-29 2021  52    2021-12-26 2021-12-27 2021-12-28 2021-12-29 2021-12-30 2021-12-31
 5 2021-12-30 2021  52    2021-12-26 2021-12-27 2021-12-28 2021-12-29 2021-12-30 2021-12-31
 6 2021-12-31 2021  52    2021-12-26 2021-12-27 2021-12-28 2021-12-29 2021-12-30 2021-12-31
 7 2022-01-01 2021  52    2021-12-26 2021-12-27 2021-12-28 2021-12-29 2021-12-30 2021-12-31
 8 2022-01-02 2021  52    2021-12-26 2021-12-27 2021-12-28 2021-12-29 2021-12-30 2021-12-31
 9 2022-01-03 2022  01    2022-01-02 2022-01-03 2022-01-04 2022-01-05 2022-01-06 2022-01-07
10 2022-01-04 2022  01    2022-01-02 2022-01-03 2022-01-04 2022-01-05 2022-01-06 2022-01-07
11 2022-01-05 2022  01    2022-01-02 2022-01-03 2022-01-04 2022-01-05 2022-01-06 2022-01-07
# ... with 1 more variable: 6 <date>

将日期转换为年份和周数并返回

Converting date to year and week number and back

format

r

date

data-conversion