我在将POSIXct转换为字符并在R中的POSIXct中转换时遇到问题。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年的时间戳，从夏令时（CEST）到夏令时（CET）的夏时制发生了（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：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"
例如，当通过这些时间戳合并对象时，这会导致许多问题。有办法解决这个问题吗？
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
最佳答案
这是从POSIXct到character再回到POSIXct的一种变通方法，可以保留原始的夏令时状态。
Sys.setenv(TZ='Europe/Berlin') # to reproduce OP's example
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_02_lt <- as.POSIXlt(time_seq_02)
time_seq_02_lt$isdst <- as.POSIXlt(time_seq_01)$isdst
time_seq_03 <- as.POSIXct(time_seq_02_lt)
据我所知，R对字符串到日期时间的支持不包括在字符串中指定的DST标志。
关于r - R中的字符POSIXct转换在夏时制转换(CEST/CET)时会导致错误的时区值，我们在Stack Overflow上找到一个类似的问题：https://stackoverflow.com/questions/13156836/