如何将某一天的时间（不是 minutes/seconds 等，只是时间，例如 17:30:00）添加到 R 中的 POSIXct 日期列表中？

Question

我有一个由日期和时间组成的数据，格式为 POSIXct，如下所示：

> DayandTime
             date_time
1  2015-10-01 11:13:25
2  2015-10-01 12:38:09
3  2015-10-01 17:12:00
4  2015-10-02 11:44:05
5  2015-10-05 13:45:07
6  2015-10-05 14:53:31
7  2015-10-06 11:54:54
8  2015-10-06 16:29:22
9  2015-10-06 18:30:46
10 2015-10-07 08:41:35
11 2015-10-07 09:02:12
12 2015-10-07 10:50:25
13 2015-10-07 11:29:25
14 2015-10-07 11:49:22
15 2015-10-07 13:35:27
16 2015-10-07 15:01:17
17 2015-10-08 11:02:12
18 2015-10-08 12:03:50
19 2015-10-08 14:24:16
20 2015-10-08 14:28:31

对于每一天，我都需要添加 17.30 作为收盘时间或 end_time - 在某一天。例如，对于01 October, 2015，结束时间是October, 2015 17:30:00

示例输出如下所示：

             date_time                   end_time
1  2015-10-01 11:13:25        2015-10-01 17:30:00
2  2015-10-01 12:38:09        2015-10-01 17:30:00
3  2015-10-01 17:12:00        2015-10-01 17:30:00
4  2015-10-02 11:44:05        2015-10-02 17:30:00
5  2015-10-05 13:45:07        2015-10-05 17:30:00
6  2015-10-05 14:53:31        2015-10-05 17:30:00
7  2015-10-06 11:54:54        2015-10-06 17:30:00
8  2015-10-06 16:29:22        2015-10-06 17:30:00
9  2015-10-06 18:30:46        2015-10-06 17:30:00
10 2015-10-07 08:41:35        2015-10-07 17:30:00
11 2015-10-07 09:02:12        2015-10-07 17:30:00
12 2015-10-07 10:50:25        2015-10-07 17:30:00
13 2015-10-07 11:29:25        2015-10-07 17:30:00
14 2015-10-07 11:49:22        2015-10-07 17:30:00
15 2015-10-07 13:35:27        2015-10-07 17:30:00
16 2015-10-07 15:01:17        2015-10-07 17:30:00
17 2015-10-08 11:02:12        2015-10-08 17:30:00
18 2015-10-08 12:03:50        2015-10-08 17:30:00
19 2015-10-08 14:24:16        2015-10-08 17:30:00
20 2015-10-08 14:28:31        2015-10-08 17:30:00

为每个元素添加小时、分钟或秒听起来很简单，但结果并非预期的那样。

structure(list(date_time = structure(c(1443678205, 1443683289, 
1443699720, 1443766445, 1444032907, 1444037011, 1444112694, 1444129162, 
1444136446, 1444187495, 1444188732, 1444195225, 1444197565, 1444198762, 
1444205127, 1444210277, 1444282332, 1444286030, 1444294456, 1444294711
), class = c("POSIXct", "POSIXt"), tzone = "")), .Names = "date_time", row.names = c(NA, 
-20L), class = "data.frame")

Answer 1

这个怎么样

将 Datetime 转换为 Date，然后 Concat 所需的时间：

DayandTime$end_time <- as.POSIXct(paste(as.Date(as.POSIXct(DayandTime$date_time)), '17:30:00'))

如何将某一天的时间（不是 minutes/seconds 等，只是时间，例如 17:30:00）添加到 R 中的 POSIXct 日期列表中？

How to add time (not minutes/seconds etc, just time E.g., 17:30:00) for one particular day to a list of POSIXct dates in R?

r

posixct

difftime