我想将日期转换为年份和周数的组合。后来我想再次转换回日期。我不明白为什么不能在相同的原始日期返回，即使我尝试了所有不同的开始日期：
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
答案 0 :(得分：0)
现在，您将 newDate 设置为等于特定年份、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")
答案 1 :(得分：0)
%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>