我在将 POSIXct 转换为字符并返回到 R 中的 POSIXct 时遇到问题。我运行以下代码:
time_seq_01 <- seq(as.POSIXct("2012-10-28 02:00:00"), by = 900, length.out = 10)
time_seq_02 <- as.character(time_seq_01)
time_seq_03 <- as.POSIXct(time_seq_02)
或同等学历:
time_seq_01 <- seq(as.POSIXct("2012-10-28 02:00:00"), by = 900, length.out = 10)
time_seq_02 <- format(time_seq_01,usetz = TRUE)
time_seq_03 <- as.POSIXct(time_seq_02)
这是 2012 年中欧夏令时 (CEST)到中欧时间 (CET)的夏令时转换发生时的时间戳(10 月的最后一个星期日 02:00 - 03:00)。
当我调用这些元素时,我得到
time_seq_01
[1] "2012-10-28 02:00:00 CEST" "2012-10-28 02:15:00 CEST"
[3] "2012-10-28 02:30:00 CEST" "2012-10-28 02:45:00 CEST"
[5] "2012-10-28 02:00:00 CET" "2012-10-28 02:15:00 CET"
[7] "2012-10-28 02:30:00 CET" "2012-10-28 02:45:00 CET"
[9] "2012-10-28 03:00:00 CET" "2012-10-28 03:15:00 CET"
time_seq_02
[1] "2012-10-28 02:00:00 CEST" "2012-10-28 02:15:00 CEST"
[3] "2012-10-28 02:30:00 CEST" "2012-10-28 02:45:00 CEST"
[5] "2012-10-28 02:00:00 CET" "2012-10-28 02:15:00 CET"
[7] "2012-10-28 02:30:00 CET" "2012-10-28 02:45:00 CET"
[9] "2012-10-28 03:00:00 CET" "2012-10-28 03:15:00 CET"
time_seq_03
[1] "2012-10-28 02:00:00 CEST" "2012-10-28 02:15:00 CEST"
[3] "2012-10-28 02:30:00 CEST" "2012-10-28 02:45:00 CET"
[5] "2012-10-28 02:00:00 CEST" "2012-10-28 02:15:00 CEST"
[7] "2012-10-28 02:30:00 CEST" "2012-10-28 02:45:00 CET"
[9] "2012-10-28 03:00:00 CET" "2012-10-28 03:15:00 CET"
POSIXct 序列的创建确实可以正常工作(time_seq_01
),也可以转换为字符(time_seq_02
)。但是,从字符返回到 POSIXct 的转换会产生错误的时区 (CET/CEST) 值 ( time_seq_03
)。当对这些元素进行排序时,可以清楚地看到这一点:
sort(time_seq_01)
[1] "2012-10-28 02:00:00 CEST" "2012-10-28 02:15:00 CEST"
[3] "2012-10-28 02:30:00 CEST" "2012-10-28 02:45:00 CEST"
[5] "2012-10-28 02:00:00 CET" "2012-10-28 02:15:00 CET"
[7] "2012-10-28 02:30:00 CET" "2012-10-28 02:45:00 CET"
[9] "2012-10-28 03:00:00 CET" "2012-10-28 03:15:00 CET"
sort(time_seq_03)
[1] "2012-10-28 02:00:00 CEST" "2012-10-28 02:00:00 CEST"
[3] "2012-10-28 02:15:00 CEST" "2012-10-28 02:15:00 CEST"
[5] "2012-10-28 02:30:00 CEST" "2012-10-28 02:30:00 CEST"
[7] "2012-10-28 02:45:00 CET" "2012-10-28 02:45:00 CET"
[9] "2012-10-28 03:00:00 CET" "2012-10-28 03:15:00 CET"
这会导致许多问题,例如在按这些时间戳合并对象时。有没有办法克服这个问题?
我使用的系统:
Windows 7 64bit
R version 2.15.1 (2012-06-22)
Platform: x86_64-pc-mingw32/x64 (64-bit)
locale:
[1] LC_COLLATE=German_Austria.1252 LC_CTYPE=German_Austria.1252
[3] LC_MONETARY=German_Austria.1252 LC_NUMERIC=C
[5] LC_TIME=German_Austria.1252
attached base packages:
[1] tools stats graphics grDevices utils datasets methods
[8] base
other attached packages:
[1] pkgtools_0.1-3 roxygen2_2.2.2 digest_0.5.2 rj_1.1.0-4
loaded via a namespace (and not attached):
[1] brew_1.0-6 plyr_1.7.1 rj.gd_1.1.0-1 stringr_0.6.1