将日期格式更改为"%d/%m/%Y"

Question

想要改变日期格式。我的数据框如下所示，想要将所有日期格式更改为"%d/%m/%Y"。

df:

id    bdate       wdate        ddate
1   09/09/09    12/10/09     2009-09-27

- Bazon

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取决于你的data.frame中实际包含了什么数据类型。这些字段是Date、character还是factor？如果你想要改变data.frame打印的方式，那么可以重载其中一个print方法（print.Date或print.POSIXlt）。 - Marek

嗨Marek，这些是日期！Bazon - Bazon

Answer 1

df$ddate <- format(as.Date(df$ddate), "%d/%m/%Y")

- Brani

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但是类别变成了字符。我该如何保持类别为日期？ - Daman deep

Answer 2

df$ddate<-strftime(df$ddate,"%d/%m/%Y")
df$bdate<-strftime(strptime(df$bdate,"%d/%m/%y"),"%d/%m/%Y")
df$wdate<-strftime(strptime(df$wdate,"%d/%m/%y"),"%d/%m/%Y")

- James

Answer 3

默认情况下，R会将字符串视为因子。当然，个人设置可能与默认设置不同。更好的做法是将变量值更改为字符，然后将其转换为日期。我经常使用chron包-它很好用、简单而且最重要的是，它能够胜任任务。这个包唯一的缺点在于时区处理。

如果您没有安装chron，请执行以下操作：

 install.packages("chron")
 # load it
 library(chron)
 # make dummy data
 bdate <- c("09/09/09", "12/05/10", "23/2/09")
 wdate <- c("12/10/09", "05/01/07", "19/7/07")
 ddate <- c("2009-09-27", "2007-05-18", "2009-09-02")
 # notice the last argument, it will not allow creation of factors!
 dtf <- data.frame(id = 1:3, bdate, wdate, ddate, stringsAsFactors = FALSE)
 # since we have characters, we can do:
 foo <- transform(dtf, bdate = chron(bdate, format = "d/m/Y"), wdate = chron(wdate, format = "d/m/Y"), ddate = chron(ddate, format = "y-m-d"))
 # check the classes
 sapply(foo, class)
 # $id
 # [1] "integer"

 # $bdate
 # [1] "dates" "times"

 # $wdate
 # [1] "dates" "times"

 # $ddate
 # [1] "dates" "times"

就是这样...这应该能解决问题...

- aL3xa