R：当我尝试格式化日期字符串时，为什么strptime总是返回NA？ [英] R: Why does strptime always return NA when I try to format a date string?

问题描述

这是我的一些数据，从文件名AttReport_all中读取：

Here's some of my data, read in from a file names AttReport_all:

Registration.Date                 Join.Time                Leave.Time
1 Jul 05, 2011 09:30 PM EDT Jul 07, 2011 01:05 PM EDT Jul 07, 2011 01:53 PM EDT
2 Jul 05, 2011 10:20 AM EDT Jul 07, 2011 01:04 PM EDT Jul 07, 2011 01:53 PM EDT
3 Jul 04, 2011 02:41 PM EDT Jul 07, 2011 12:49 PM EDT Jul 07, 2011 01:53 PM EDT
4 Jul 04, 2011 11:38 PM EDT Jul 07, 2011 12:49 PM EDT Jul 07, 2011 01:54 PM EDT
5 Jul 05, 2011 11:41 AM EDT Jul 07, 2011 12:54 PM EDT Jul 07, 2011 01:54 PM EDT
6 Jul 07, 2011 11:08 AM EDT Jul 07, 2011 01:16 PM EDT Jul 07, 2011 01:53 PM EDT

如果我做 strptime（AttReport_all $ Registration.Date，％b％m，％Y％H：％ M％p，tz =）我得到一个我期待日期的NAs数组。

If I do strptime(AttReport_all$Registration.Date, "%b %m, %Y %H:%M %p", tz="") I get an array of NAs where I'm expecting dates.

Sys.setlocale（LC_TIME，C）返回C

typeof（AttReport_all $ Registration日期） re转为整数

is.factor（AttReport_all $ Registration.Date）返回TRUE。

我缺少什么？

这里是版本输出，如果有帮助：
platform i386- pc-mingw32

arch i386

os mingw32

system i386，mingw32

status

major 2 < br>
minor 13.0

year 2011

month 04

day 13

svn rev 55427

语言R

version.string R版本2.13.0（2011-04-13）

Here's version output, if it helps: platform i386-pc-mingw32
arch i386
os mingw32
system i386, mingw32
status
major 2
minor 13.0
year 2011
month 04
day 13
svn rev 55427
language R
version.string R version 2.13.0 (2011-04-13)

推荐答案

strptime 在第一个参数上自动运行 as.character （所以这并不重要，这是一个因素） format = 中未指定的尾随字符将被忽略（因此EDT无关紧要）。

strptime automatically runs as.character on the first argument (so it doesn't matter that it's a factor) and any trailing characters not specified in format= are ignored (so "EDT" doesn't matter).

只有问题是打印机@Ben Bolker识别（％m 应该是％d ）和 ％H 应该是％I （？strptime 说你应该不使用％H 与％p ）。

The only issues are the typo @Ben Bolker identified (%m should be %d) and %H should be %I (?strptime says you should not use %H with %p).

# %b and %m are both *month* formats
strptime("Jul 05, 2011 09:30 PM EDT", "%b %m, %Y %H:%M %p", tz="")
# [1] NA

# change %m to %d and we no longer get NA, but the time is wrong (AM, not PM)
strptime("Jul 05, 2011 09:30 PM EDT", "%b %d, %Y %H:%M %p", tz="")
# [1] "2011-07-05 09:30:00"

# use %I (not %H) with %p
strptime("Jul 05, 2011 09:30 PM EDT", "%b %d, %Y %I:%M %p", tz="")
# [1] "2011-07-05 21:30:00"

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