R - 给定奥尔森时区的 UTC 到 LOCAL 时间

我有 1974-2013 年的时间序列数据，其中有一列为 datetimeUTC (YYYY-MM-DD hh:mm +0000)，一列为 Olson 格式的时区（例如，加拿大/太平洋、加拿大/东部）。我可以将整个 UTCdatetime 列转换为公共时区，如下所示：

dataset$datetimeEST <- strptime(
  dataset$datetimeUTC, format="%Y-%m-%d %H:%M:%S%z", tz="Canada/Eastern"
)  

我如何转换datetimeUTC to datetimeLOCAL，给定每行相应的时区？

让我退后一点。我有来自全国各地（6 个时区）的数据，格式为 1974-2013 年的 ISO8601 表示形式。时间戳全年均采用当地标准时间（即，即使该地区的民用时间遵守 DST，也将忽略 DST）。我需要进行日期时间计算，这在 UTC 时间中可能是最安全的，所以这很容易。但是，我还需要提取特定民用时间段的数据，考虑 DST，并为该子集数据进行计算和绘图（例如，所有 6 个时区位置的高峰时间的所有数据）。

我在下面计算的 datetimeCLOCKTIME 似乎正在做我想要的绘图，但在进行日期时间计算时给出了错误的答案，因为它将日期时间存储在我的本地计算机的时区中，而没有实际转换时间。 @thelatemail 提供的解决方案正是我正在寻找的，但我无法让它在 Windows 中的 2012 年测试数据集上运行（见下文）。另外，我使用 strptime 转换为 POXITlt，他的解决方案在 POXITct 中。我是 R 新手，因此我们将不胜感激任何帮助。

测试数据集：

    dataset <- data.frame (timestampISO8601 = c("2012-04-25T22:00:00-08:00","2012-04-25T22:15:00-08:00","2012-04-25T22:30:00-08:00","2012-04-25T22:45:00-08:00","2012-04-25T23:00:00-08:00","2012-04-25T23:15:00-08:00","2012-04-25T23:30:00-08:00","2012-04-25T23:45:00-08:00","2012-04-26T00:00:00-08:00","2012-04-26T00:15:00-08:00","2012-04-26T00:30:00-08:00","2012-04-26T00:45:00-08:00","2012-04-26T01:00:00-08:00","2012-04-26T01:15:00-08:00","2012-04-26T01:30:00-08:00","2012-04-26T01:45:00-08:00","2012-04-26T02:00:00-08:00","2012-04-25T22:00:00-03:30","2012-04-25T22:15:00-03:30","2012-04-25T22:30:00-03:30","2012-04-25T22:45:00-03:30","2012-04-25T23:00:00-03:30","2012-04-25T23:15:00-03:30","2012-04-25T23:30:00-03:30","2012-04-25T23:45:00-03:30","2012-04-26T00:00:00-03:30","2012-04-26T00:15:00-03:30","2012-04-26T00:30:00-03:30","2012-04-26T00:45:00-03:30","2012-04-26T01:00:00-03:30","2012-04-26T01:15:00-03:30","2012-04-26T01:30:00-03:30","2012-04-26T01:45:00-03:30","2012-04-26T02:00:00-03:30"), olson = c("Canada/Pacific","Canada/Pacific","Canada/Pacific","Canada/Pacific","Canada/Pacific","Canada/Pacific","Canada/Pacific","Canada/Pacific","Canada/Pacific","Canada/Pacific","Canada/Pacific","Canada/Pacific","Canada/Pacific","Canada/Pacific","Canada/Pacific","Canada/Pacific","Canada/Pacific","Canada/Newfoundland","Canada/Newfoundland","Canada/Newfoundland","Canada/Newfoundland","Canada/Newfoundland","Canada/Newfoundland","Canada/Newfoundland","Canada/Newfoundland","Canada/Newfoundland","Canada/Newfoundland","Canada/Newfoundland","Canada/Newfoundland","Canada/Newfoundland","Canada/Newfoundland","Canada/Newfoundland","Canada/Newfoundland","Canada/Newfoundland"), value = c(0,0,1,2,5,11,17,19,20,19,17,11,5,2,1,0,0,-3,-3,-2,-1,2,8,14,16,17,16,14,8,2,-1,-2,-3,-3), stringsAsFactors=FALSE)

从 UTC 偏移量中删除“:”。 （R 期望 UTC 偏移量的格式为 nnnn）：

    dataset$timestampR<- paste(substr(dataset$timestampISO8601,1,22),substr(dataset$timestampISO8601,24,25),sep="")

当转换为 UTC 时间时，R 默认为 UTC 偏移量 -ve，使时间戳中的 -ve 偏移量为正：

    dataset$datetimeUTC <- strptime(dataset$timestampR, format="%Y-%m-%dT%H:%M:%S%z", tz="UTC")

当像这样转换为机器时间时，R 读取输入时间并将其转换为本地机器时区的时间 - 在我的例子中，这是加拿大/东部：

    dataset$datetimeMACHINE <- strptime(dataset$timestampR, format="%Y-%m-%dT%H:%M:%S%z")

当像这样转换为 CLOCKTIME 时间时，R 读取输入时间并分配本地计算机的时区（当前在我的计算机上为 EDT），而不进行任何时间转换：

    dataset$datetimeCLOCKTIME <- strptime(dataset$timestampR,format="%Y-%m-%dT%H:%M:%S")

查看数据集的结构：

    str(dataset)  

绘图行为不同

    library(ggplot2)
    qplot(data=dataset,x=datetimeUTC,y=value)
    qplot(data=dataset,x=datetimeMACHINE,y=value)
    qplot(data=dataset,x=datetimeCLOCKTIME,y=value)

计算结果不同。 datetimeCLOCKTIME 的计算结果不正确：

    range (dataset$datetimeUTC)
    range (dataset$datetimeMACHINE)
    range (dataset$datetimeCLOCKTIME)

    dataset$datetimeUTC[34] - dataset$datetimeUTC[1]
    dataset$datetimeMACHINE[34] - dataset$datetimeMACHINE[1]
    dataset$datetimeCLOCKTIME[34] - dataset$datetimeCLOCKTIME[1]

您可以来回格式化一下以获得字符格式的本地时间表示形式。例如。：

dataset <- data.frame(
  datetimeUTC=c("2014-01-01 00:00 +0000","2014-01-01 00:00 +0000"),
  olson=c("Canada/Eastern", "Canada/Pacific"),
  stringsAsFactors=FALSE
)

#             datetimeUTC          olson
#1 2014-01-01 00:00 +0000 Canada/Eastern
#2 2014-01-01 00:00 +0000 Canada/Pacific

dataset$localtime <- with(dataset, 
     mapply(function(dt,ol) format(
              as.POSIXct(dt,"%Y-%m-%d %H:%M %z",tz=ol),
              "%Y-%m-%d %H:%M %z"), 
              datetimeUTC, olson
            )
     )

#             datetimeUTC          olson              localtime
#1 2014-01-01 00:00 +0000 Canada/Eastern 2013-12-31 19:00 -0500
#2 2014-01-01 00:00 +0000 Canada/Pacific 2013-12-31 16:00 -0800