R根据最近的日期和时间匹配合并两个数据框[重复]

Question

我已经看到这个问题的各种解决方案仅基于日期，但时间部分让我感到困惑。我有两个带有 POSIXct 列的数据框，称为“日期时间”。对于 DF1，该列的数据四舍五入到最接近的小时。对于 DF2，时间分量不四舍五入到最接近的小时，并且可以随时发生。数据框如下所示：

DF1

datetime	X	Y	Z
2020-09-01 03:00:00	1	3	4
2020-09-02 12:00:00	12	3	5
2020-09-02 22:00:00	4	9	19
2020-09-03 01:00:00	4	10	2
2020-09-04 06:00:00	4	12	1
2020-09-04 08:00:00	11	13	10

DF2

datetime	Var
2020-09-01 02:23:14	A
2020-09-01 03:12:09	B
2020-09-02 11:52:15	A
2020-09-02 12:15:44	B
2020-09-02 22:31:56	A
2020-09-02 21:38:05	B
2020-09-03 01:11:39	A
2020-09-03 00:59:33	B
2020-09-04 05:12:19	A
2020-09-04 06:07:09	B
2020-09-04 08:22:28	A
2020-09-04 07:50:17	B

我想要的是基于此列使用与 DF1 中的“日期时间”最接近的日期和时间合并这两个数据帧，使其看起来像这样：

datetime	X	Y	Z	Var
2020-09-01 03:00:00	1	3	4	B
2020-09-02 12:00:00	12	3	5	A
2020-09-02 22:00:00	4	9	19	B
2020-09-03 01:00:00	4	10	2	B
2020-09-04 06:00:00	4	12	1	B
2020-09-04 08:00:00	11	13	10	B

谢谢！

Answer 1

为merge 和group_by 添加辅助列，使用merge 然后dplyr 进行过滤

library(dplyr)

df1$tmp <- as.Date(df1$datetime)
df2$tmp <- as.Date(df2$datetime)

df1$grp <- 1:(nrow(df1))

merge(df1, df2, "tmp") %>% 
  group_by(grp) %>% 
  slice(which.min(abs(difftime(datetime.x, datetime.y)))) %>% 
  ungroup() %>% 
  select(-c(tmp,grp,datetime.y))
# A tibble: 6 × 5
  datetime.x              X     Y     Z Var  
  <chr>               <int> <int> <int> <chr>
1 2020-09-01 03:00:00     1     3     4 B    
2 2020-09-02 12:00:00    12     3     5 A    
3 2020-09-02 22:00:00     4     9    19 B    
4 2020-09-03 01:00:00     4    10     2 B    
5 2020-09-04 06:00:00     4    12     1 B    
6 2020-09-04 08:00:00    11    13    10 B

数据

df1 <- structure(list(datetime = c("2020-09-01 03:00:00", "2020-09-02 12:00:00", 
"2020-09-02 22:00:00", "2020-09-03 01:00:00", "2020-09-04 06:00:00", 
"2020-09-04 08:00:00"), X = c(1L, 12L, 4L, 4L, 4L, 11L), Y = c(3L, 
3L, 9L, 10L, 12L, 13L), Z = c(4L, 5L, 19L, 2L, 1L, 10L)), class = "data.frame", row.names = c(NA, 
-6L))

df2 <- structure(list(datetime = c("2020-09-01 02:23:14", "2020-09-01 03:12:09", 
"2020-09-02 11:52:15", "2020-09-02 12:15:44", "2020-09-02 22:31:56", 
"2020-09-02 21:38:05", "2020-09-03 01:11:39", "2020-09-03 00:59:33", 
"2020-09-04 05:12:19", "2020-09-04 06:07:09", "2020-09-04 08:22:28", 
"2020-09-04 07:50:17"), Var = c("A", "B", "A", "B", "A", "B", 
"A", "B", "A", "B", "A", "B")), class = "data.frame", row.names = c(NA, 
-12L))