R:如何获取时间序列数据中datetime列的最大值 [英] R: How to get the maximum value of a datetime column in a time series data

问题描述

我正在处理时间序列数据.我有2个日期时间列和1个财政周列.我举了一个例子，说明我的情况如下，我需要获得EditDate的最大值.

I am working on a time series data. I have 2 date time columns and 1 fiscal week column. I have given an example where I have a situation like below and I need to get the MAX of the EditDate.

EditDate <- c("2015-04-01 11:40:13", "2015-04-03 02:54:45","2015-04-07 11:40:13")
ID <- c("DL1X8", "DL1X8","DL1X8")
Avg <- c(38.1517, 38.1517, 38.1517)
Sig <- c(11.45880000, 11.45880000, 11.45880000)
InsertDate <- c("2015-04-03 9:40:00", "2015-04-03 9:40:00",2015-04-10 9:40:00)
FW <- c("39","39","40")

df1 <- data.frame(EditDate , ID, Avg, Sig, InsertDate, FW)

这将返回

+---------------------+-------+---------+-------------+--------------------+----+
|   EditDate          | ID    | Avg     |   Sig       |    InsertDate      | FW |
+---------------------+-------+---------+-------------+--------------------+----+
| 2015-04-01 11:40:13 | DL1X8 | 38.1517 | 11.45880000 | 2015-04-03 9:40:00 | 39 |
| 2015-04-03 02:54:45 | DL1X8 | 38.1517 | 11.45880000 | 2015-04-03 9:40:00 | 39 |
| 2015-04-07 11:40:13 | DL1X8 | 38.1517 | 11.45880000 | 2015-04-10 9:40:00 | 40 |
+---------------------+-------+---------+-------------+--------------------+----+

我想要的期望输出是

+---------------------+-------+---------+-------------+--------------------+----+
|   EditDate          | ID    | Avg     |   Sig       |    InsertDate      | FW |
+---------------------+-------+---------+-------------+--------------------+----+
| 2015-04-07 11:40:13 | DL1X8 | 38.1517 | 11.45880000 | 2015-04-10 9:40:00 | 40 |
+---------------------+-------+---------+-------------+--------------------+----+

我尝试使用带库(RH2)的sqldf来运行，但是运行需要很多时间.

I tried using sqldf using the library(RH2) but it takes a lot of time to run.

df2 <- sqldf("SELECT * FROM df1 
                        WHERE (EditDate = (SELECT MAX(EditDate) FROM df1))
                        ORDER BY EditDate ASC")

我不确定是否可以使用dplyr软件包来完成.有人可以提供有关我如何使用dplyr或任何其他替代方案进行优化的意见吗?

I am not sure if it could be done using the dplyr package. Could someone provide inputs on how I could optimize this using dplyr or any other alternatives?

推荐答案

这里是一个底数为R的班轮

Here's one liner with base R

df1[which.max(as.POSIXct(df1$InsertDate)), ]
#              EditDate    ID     Avg     Sig         InsertDate FW
# 3 2015-04-07 11:40:13 DL1X8 38.1517 11.4588 2015-04-10 9:40:00 40

或使用data.table

library(data.table)
setDT(df1)[which.max(as.POSIXct(InsertDate))]
#               EditDate    ID     Avg     Sig         InsertDate FW
# 1: 2015-04-07 11:40:13 DL1X8 38.1517 11.4588 2015-04-10 9:40:00 40

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