Question

我有1974 - 2013年的时间序列数据，其中包含datetimeUTC（YYYY-MM-DD hh：mm +0000）的列，以及Olson格式的时区列（例如，加拿大/太平洋，加拿大/东部）。我可以将整个UTCdatetime列转换为这样的公共时区：

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

如果每行中有相应的时区，如何将datetimeUTC转换为datetimeLOCAL？

让我回顾一下。我有来自全国各地的数据（6个时区），格式为ISO 8601表示1974-2013。时间戳是全年的当地标准时间（即，即使该地区的平民时间遵守DST，也会忽略DST）。我需要进行日期时间计算，这在UTC时间可能是最安全的，所以这很容易。但是，我还需要考虑DST来提取特定民用时段的数据，并针对该子集化数据进行计算和绘图（例如，所有6个时区中的高峰时段的所有数据）。

我在下面计算的datetimeCLOCKTIME似乎正在执行我想要的绘图，但是在进行日期时间计算时会给出错误的答案，因为它将日期时间存储在本地计算机的时区中而没有实际转换时间。 @thelatemail提供的解决方案是我正在寻找的解决方案，但我还没有能够在2012年的测试数据集中使用Windows（见下文）。另外，我使用strptime转换为POXITlt，他的解决方案是POXITct。我是R的新手，所以任何帮助都会受到无限的赞赏。

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)

删除＆＃34;：＆＃34;来自UTC偏移量。（R期望UTC偏移的格式为nnnn）：

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

转换为UTC时间时，R默认为UTC偏移的-ve，使时间戳中的-ve偏移为正：

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

当像这样转换到MACHINE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 - 在我的情况下，这是加拿大/东部：

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

当像这样转换到CLOCKTIME时，R读取输入时间并分配本地机器的时区（当前在我的机器上为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]

Answer 1

您可以来回格式化以获得字符格式的本地时间表示。 E.g：

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

Answer 2

如果您只有两个时区可以转换并知道UTC与这两者之间的时差。使用@ thelatemail＆＃39; s dataset

transform(dataset, 
localtime=as.POSIXct(datetimeUTC, "%Y-%m-%d %H:%M %z")-
           c(5*3600,8*3600)[as.numeric(factor(olson))])
 #            datetimeUTC          olson           localtime
#1 2014-01-01 00:00 +0000 Canada/Eastern 2013-12-31 19:00:00
#2 2014-01-01 00:00 +0000 Canada/Pacific 2013-12-31 16:00:00

R - 给定Olson时区的UTC到LOCAL时间

2 个答案: