使用带有特殊时区格式的 strptime %z [英] Using strptime %z with special timezone format

问题描述

我正在处理从 Teradata 导出的 .csv 数据.几列最初是带时区的时间戳，因此在 R 中加载 .csv 后，我想将这些列(作为字符串加载)转换为 POSIXlt 或 POSIXct.我正在使用 strptime，但 .csv 文件中的时区格式与 strptime 期望的不匹配.例如，它需要 -0400，但 .csv 的格式为 -04:00，其中冒号分隔小时和分钟.

I am working with .csv data that was exported from Teradata. Several columns were originally timestamps with timezones, so after loading the .csv in R I'd like to convert these columns (which are loaded as strings) to POSIXlt or POSIXct. I am using strptime, but the format of the timezone from the .csv file does not match what strptime is expecting. For example, it expects -0400 but the .csv has the format -04:00 where a colon separates the hours and minutes.

我可以去掉冒号，但这是一个额外的步骤和并发症，如果可能的话我想避免.有没有办法告诉 strptime 使用不同的时区格式 (%z)?

I can remove the colon, but this is an extra step and complication I'd like to avoid if possible. Is there a way to tell strptime to use a different format for the timezone (%z)?

这是一个例子:

## Example data:
x <- c("2011-10-12 22:17:13.860746-04:00", "2011-10-12 22:17:13.860746+00:00")
format <- "%Y-%m-%d %H:%M:%OS%z"

## Doesn't work:
strptime(x,format)
## [1] NA NA

## Ignores the timezone:
as.POSIXct(x)
## [1] "2011-10-12 22:17:13 EDT" "2011-10-12 22:17:13 EDT"

## Remove the last colon:
x2 <- gsub("(.*):", "\\1", x)
x2
## [1] "2011-10-12 22:17:13.860746-0400" "2011-10-12 22:17:13.860746+0000"

## This works, but requires extra processing (removing the colon)
strptime(x2,format)
## [1] "2011-10-12 22:17:13" "2011-10-12 18:17:13"

所以我希望使用诸如 strptime(x,"%Y-%m-%d %H:%M:%OS%zz") 之类的方法来实现最后一个结果，其中%zz 是用于识别 -04:00 格式的时区的自定义表达式.或者 %zH:%zM 可能会更好.

So I'm looking to achieve this last result using something like strptime(x,"%Y-%m-%d %H:%M:%OS%zz"), where %zz is a custom expression for the timezone that recognizes the -04:00 format. Or %zH:%zM might be even better.

如果这是不可能的，是否有人有将字符串(各种格式)转换为 data.frame/data.table 多列的日期的巧妙/灵活的功能?

If this isn't possible, does anyone have a slick/flexible function for converting strings (of various formats) to dates for multiple columns of a data.frame/data.table?

推荐答案

事实证明 lubridate 可以处理这种格式:

It turns out lubridate can handle this format:

library(lubridate)
ymd_hms(x)
## [1] "2011-10-13 02:17:13 UTC" "2011-10-12 22:17:13 UTC"

或者，以本地时区显示:

Or, to display in the local timezone:

with_tz(ymd_hms(x))
## [1] "2011-10-12 22:17:13 EDT" "2011-10-12 18:17:13 EDT"

为了获得更大的灵活性(仍然使用 lubridate):

For more flexibility (still using lubridate):

parse_date_time(x, "%Y-%m-%d %H:%M:%OS%z")

为了更快的速度(在 lubridate 选项中):

For faster speed (amongst lubridate options):

lubridate:::.strptime(x, "%Y-%m-%d %H:%M:%OS%OO")

时间:

microbenchmark(
  ymd_hms(x),
  parse_date_time(x, "%Y-%m-%d %H:%M:%OS%z"),
  lubridate:::.strptime(x, "%Y-%m-%d %H:%M:%OS%OO"),
  strptime(gsub("(.*):", "\\1", x), format)
)

## Unit: microseconds
##                                               expr      min       lq       mean    median        uq      max neval
##                                         ymd_hms(x) 1523.819 1578.495 1715.14577 1629.5385 1744.3695 2850.393   100
##         parse_date_time(x, "%Y-%m-%d %H:%M:%OS%z") 1108.676 1150.633 1273.77301 1190.3315 1264.8050 5947.204   100
##  lubridate:::.strptime(x, "%Y-%m-%d %H:%M:%OS%OO")   89.838  103.390  112.45338  107.8425  115.2265  216.512   100
##        strptime(gsub("(.*):", "\\\\1", x), format)   46.716   58.294   71.90934   69.9415   86.5860  105.044   100

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