如何在R中的循环中显示实际日期 [英] How to display real dates in a loop in r

问题描述

当我循环遍历日期时，R打印出日期的数字编码.

When I iterate over dates in a loop, R prints out the numeric coding of the dates.

例如:

dates <- as.Date(c("1939-06-10", "1932-02-22", "1980-03-13", "1987-03-17",
                    "1988-04-14", "1979-08-28", "1992-07-16", "1989-12-11"), tryFormats = c("%Y-%m-%d"))

for(d in dates){

  print(d)
}

输出如下:

[1] -11163
[1] -13828
[1] 3724
[1] 6284
[1] 6678
[1] 3526
[1] 8232
[1] 7284

如何获取R以打印出实际日期? 因此输出为:

How do I get R to print out the actual dates? So the output reads:

[1] "1939-06-10" 
[1] "1932-02-22" 
[1] "1980-03-13" 
[1] "1987-03-17" 
[1] "1988-04-14" 
[1] "1979-08-28" 
[1] "1992-07-16" 
[1] "1989-12-11"

谢谢！

推荐答案

在R的for循环中将dates用作seq时，它将丢失其属性.

When you use dates as seq in a for loop in R, it loses its attributes.

您可以使用as.vector剥离属性并自己查看(或dput看到完整对象的内幕):

You can use as.vector to strip attributes and see for yourself (or dput to see under the hood on the full object):

as.vector(dates)
# [1] -11163 -13828   3724   6284   6678   3526   8232   7284
dput(dates)
# structure(c(-11163, -13828, 3724, 6284, 6678, 3526, 8232, 7284), class = "Date")

在R中，Date对象只是具有class Date(class是属性)的numeric向量.

In R, Date objects are just numeric vectors with class Date (class is an attribute).

因此，您会看到数字(FWIW，这些数字自1970-01-01起算为天).

Hence you're seeing numbers (FWIW, these numbers count days since 1970-01-01).

要恢复Date属性，可以使用.Date函数:

To restore the Date attribute, you can use the .Date function:

for (d in dates) print(.Date(d))
# [1] "1939-06-10"
# [1] "1932-02-22"
# [1] "1980-03-13"
# [1] "1987-03-17"
# [1] "1988-04-14"
# [1] "1979-08-28"
# [1] "1992-07-16"
# [1] "1989-12-11"

这等效于as.Date(d, origin = '1970-01-01')，这是as.Date的numeric方法.

This is equivalent to as.Date(d, origin = '1970-01-01'), the numeric method for as.Date.

有趣的是，*apply函数不会去除属性:

Funnily enough, *apply functions don't strip attributes:

invisible(lapply(dates, print))
# [1] "1939-06-10"
# [1] "1932-02-22"
# [1] "1980-03-13"
# [1] "1987-03-17"
# [1] "1988-04-14"
# [1] "1979-08-28"
# [1] "1992-07-16"
# [1] "1989-12-11"

这篇关于如何在R中的循环中显示实际日期的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！