字符串到日期和时间使用R

Question

我有大约 400,000 行的以下格式的日期和时间测验截止日期和提交时间。日期和时间是字符：

  Lesson<-data.table(Quiz = c(1:5), 
  Duedate=c("2015-07-29 08:00", "2015-08-05 08:00","2015-08-12 08:00", "2015-08-19 08:00", "2015-08-26 08:00"),
  Datecomp=c("2015-07-30 21:00", "2015-08-04 13:00","2015-08-12 07:59", "2015-08-19 10:00", "2015-08-16 23:00"))

我需要将其转换为日期和时间格式以使用

我尝试过使用

library(lubridate)
Lesson$Duedate<-as.Date(Lesson$Duedate,"%Y-%m-%d %H:%M")

但这会减少我需要的时间。

我也试过strptime如下：

Lesson$Datecomp<-strptime(Lesson$Datecomp, "%Y%m%d %H%M")

但我收到以下错误消息：

   Warning messages:
  1: In `[<-.data.table`(x, j = name, value = value) :
    Supplied 11 items to be assigned to 5 items of column 'Datecomp' (6 unused)
  2: In `[<-.data.table`(x, j = name, value = value) :
    Coerced 'list' RHS to 'character' to match the column's type. Either change the target column to 'list' first (by creating a new 'list' vector length 5 (nrows of entire table) and assign that; i.e. 'replace' column), or coerce RHS to 'character' (e.g. 1L, NA_[real|integer]_, as.*, etc) to make your intent clear and for speed. Or, set the column type correctly up front when you create the table and stick to it, please.

任何有关如何格式化日期和时间以及指定澳大利亚/墨尔本时间的帮助将不胜感激。

Answer 1

你想要：

Lesson$Duedate <- as.POSIXct(Lesson$Duedate, tz = "Australia/Melbourne")
Lesson$Datecomp <- as.POSIXct(Lesson$Datecomp, tz = "Australia/Melbourne")

您可以在其中添加format = "%Y-%m-%d %H:%M"，但您已经是默认格式。