使用 POSIXct 时间序列更改时区，R

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问题描述

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我在处理时间序列时遇到了麻烦 &R 中的区域，我无法弄清楚如何继续.

I've run into a trouble working with time series & zones in R, and I can't quite figure out how to proceed.

我有一个这样的时间序列数据:

I have an time series data like this:

df <- data.frame( 
  Date     = seq(as.POSIXct("2014-01-01 00:00:00"), length.out = 1000, by = "hours"),
  price    = runif(1000, min = -10, max = 125),
  wind     = runif(1000, min = 0, max = 2500),
  temp     = runif(1000, min = - 10, max = 25)  
)

现在，日期是 UTC 时间.我想对数据进行子集/过滤，例如我从今天(今天是 2014-05-13)获取值:

Now, the Date is in UTC-time. I would like to subset/filter the data, so for example I get the values from today (Today is 2014-05-13):

df[ as.Date(df$Date) == Sys.Date(), ]

但是，当我这样做时，我得到的数据以:

However, when I do this, I get data that starts with:

2014-05-13 02:00:00

而不是:

2014-05-13 00:00:00

因为我目前处于 CEST 时间，即 UTC 时间后两小时.所以我尝试更改数据:

Because im currently in CEST-time, which is two hours after UTC-time. So I try to change the data:

df$Date <- as.POSIXct(df$Date, format = "%Y-%m-%d %H", tz = "Europe/Berlin")

然而这行不通.我尝试了各种变体，例如将其剥离为字符，然后进行转换等等，但我已经把头靠在墙上，我猜我缺少一些简单的东西.

Yet this doesn't work. I've tried various variations, such as stripping it to character, and then converting and so on, but I've run my head against a wall, and Im guessing there is something simple im missing.

推荐答案

为了避免使用时区这样的问题，使用 format 来获取日期的字符表示:

To avoid using issues with timezones like this, use format to get the character representation of the date:

df[format(df$Date,"%Y-%m-%d") == Sys.Date(), ]

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