更改 POSIXct 对象中的时区 [英] Change timezone in a POSIXct object

问题描述

在 R 中使用日期时间和时区可能会很棘手.这是我的问题:我想更改 POSIXct 对象

Playing with dateTimes and timezone can be tricky in R. Here is my question: I want to change the time-zone on a POSIXct object

R) data <- data.frame(x=c(1,2),dateTime=as.POSIXct(c("2010-03-11 03:30:00.432","2010-03-15 03:30:00.432"),format="%Y-%m-%d %H:%M:%S",tz="America/Montreal"))
R) data
  x            dateTime
1 1 2010-03-11 03:30:00
2 2 2010-03-15 03:30:00
R) str(data)
'data.frame':   2 obs. of  2 variables:
 $ x       : num  1 2
 $ dateTime: POSIXct, format: "2010-03-11 03:30:00" "2010-03-15 03:30:00"

但是如果我想更改时区，我唯一发现的是:

But if I want to change the timezone, the only thing I found is:

R) data$dateTime2 = format(data$dateTime,tz="Europe/Paris")
R) str(data)
'data.frame':   2 obs. of  3 variables:
 $ x        : num  1 2
 $ dateTime : POSIXct, format: "2010-03-11 03:30:00" "2010-03-15 03:30:00"
 $ dateTime2: chr  "2010-03-11 09:30:00" "2010-03-15 08:30:00"

或

R) data$dateTime2 = as.POSIXlt(data$dateTime,tz="Europe/Paris")
R) str(data)
'data.frame':   2 obs. of  3 variables:
 $ x        : num  1 2
 $ dateTime : POSIXct, format: "2010-03-11 03:30:00" "2010-03-15 03:30:00"
 $ dateTime2: POSIXlt, format: "2010-03-11 09:30:00" "2010-03-15 08:30:00"

上帝(或 SO 上的某个人)知道为什么它不适用于 POSIXct

God (or somebody on SO) knows why it doesn't work with POSIXct

R) data$dateTime2 = as.POSIXct(data$dateTime,tz="Europe/Paris")
R) str(data)
'data.frame':   2 obs. of  3 variables:
 $ x        : num  1 2
 $ dateTime : POSIXct, format: "2010-03-11 03:30:00" "2010-03-15 03:30:00"
 $ dateTime2: POSIXct, format: "2010-03-11 03:30:00" "2010-03-15 03:30:00"

我是否需要转换为 character 并转换回 POSIXct ?

Do I need to convert to character and cast back to POSIXct ?

推荐答案

它不适用于 POSIXct 因为 base::as.POSIXct.default 只返回 x 如果它已经是 POSIXct.您可以通过 tzone 属性更改时区:

It doesn't work with POSIXct because base::as.POSIXct.default simply returns x if it's already POSIXct. You can change the timezone via the tzone attribute:

attr(data$dateTime, "tzone") <- "Europe/Paris"

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