将字符转换为日期

Question

我有一个日期的矢量,格式如下:

 dates <- c("01AUG2006","01DEC2006","01JUN2006","01MAY2007")

要将此向量转换为类的对象Date,我编写了此函数:

convert2Date <- function(x) {
  require(car)
  d <- substr(x,0,2)
  m.text <- substr(x,3,5)
  m <- Recode(m.text, "'JAN'=1 ;'FEB'=2;'MAR'=3;'APR'=4;'MAY'=5;'JUN'=6; 
                       'JUL'=7;'AUG'=8;'SEP'=9;'OCT'=10;'NOV'=11;'DEC'=12")
  y <- substr(x,6,9)
  out <- as.Date(paste(d,m,y,sep="/"),"%d/%m/%Y")
  out
}

使用示例dates变量:

test <- convert2Date(dates)
[1] "2006-08-01" "2006-12-01" "2006-06-01" "2007-05-01"
class(test)
[1] "Date"

这可行,但它看起来有点麻烦,只适用于这种特定的格式.由于这可能是一个常见问题,因此必须有一种更简单,更通用的方法.有人建议吗？非常感谢!

Answer 1

看起来好像

as.Date(dates,format="%d%b%Y")

工作良好？

[1] "2006-08-01" "2006-12-01" "2006-06-01" "2007-05-01"

Answer 2

问题是你的语言环境.就像我的一样.

我的系统是葡萄牙语

> sessionInfo()
R version 3.1.0 (2014-04-10)
Platform: x86_64-w64-mingw32/x64 (64-bit)

locale:
[1] LC_COLLATE=Portuguese_Portugal.1252  LC_CTYPE=Portuguese_Portugal.1252    LC_MONETARY=Portuguese_Portugal.1252
[4] LC_NUMERIC=C                         LC_TIME=Portuguese_Portugal.1252    

如果我只是尝试

library(lubridate)
dmy(c("01AUG2006","01DEC2006","01JUN2006","01MAY2007"))
[1] NA               NA               "2006-06-01 UTC" NA              
Warning message:
 3 failed to parse.

没有区域设置重置,lubridate::dmy如果我将Months更改为葡萄牙语abrev表单,将对我有用.

dmy(c("01AGO2006","01DEZ2006","01JUN2006","01MAI2007"))
[1] "2006-08-01 UTC" "2006-12-01 UTC" "2006-06-01 UTC" "2007-05-01 UTC"

或者从dmy函数调用设置语言环境,结果变得非常容易.

dmy(dates, locale = "English_United States.1252") # Without resetting locale
[1] "2006-08-01 UTC" "2006-12-01 UTC" "2006-06-01 UTC" "2007-05-01 UTC"

现在好了.

对于非英语系统,必须相应地更改语言环境或重写文本.

将语言环境重置为美国英语2252

Sys.setlocale(category = "LC_ALL", locale = "English_United States.1252")
dates <- c("01AUG2006","01DEC2006","01JUN2006","01MAY2007")
dmy(dates)
[1] "2006-08-01 UTC" "2006-12-01 UTC" "2006-06-01 UTC" "2007-05-01 UTC"

Date重置区域设置后,现在也一样

as.Date(dates,format="%d%b%Y")
# [1] "2006-08-01" "2006-12-01" "2006-06-01" "2007-05-01"