对象创建时间戳 [英] Object creation timestamp

问题描述

有没有办法检索对象的创建时间?

解决方案

一般情况下，您可以通过以下方式为自己创建的对象执行此操作

R>df <- data.frame(a=sample(LETTERS[1:5],10,TRUE),b=runif(10))R＞attr(df, "createdAt") <- Sys.time()R＞df乙1 乙 0.84370212 D 0.86834463 乙 0.51947914 乙 0.04804055 乙 0.56049786 C 0.19381547 0.14510778 D 0.17854059 C 0.393779510 乙 0.2874135R＞字符串(df)'data.frame':10 个观察.2个变量:$ a:具有 4 个级别A"、B"、C"、D"的因子:2 4 2 2 2 3 1 4 3 2$ b: 数字 0.844 0.868 0.519 0.048 0.56 ...- attr(*, "createdAt")= POSIXct，格式:"2011-03-16 10:42:10.137434"R＞

然后您可以自己编写一些使用该属性的自定义 print() 或 show() 函数.Frank Harrell 的 rms 和它的前身设计已经做了很长时间了.>

Is there a way to retrieve the time an object was created at?

解决方案

Not generally but you can do it for objects you create yourself via

R> df <- data.frame(a=sample(LETTERS[1:5],10,TRUE),b=runif(10))
R> attr(df, "createdAt") <- Sys.time()
R> df
   a         b
1  B 0.8437021
2  D 0.8683446
3  B 0.5194791
4  B 0.0480405
5  B 0.5604978
6  C 0.1938154
7  A 0.1451077
8  D 0.1785405
9  C 0.3937795
10 B 0.2874135
R> str(df)
'data.frame':   10 obs. of  2 variables:
 $ a: Factor w/ 4 levels "A","B","C","D": 2 4 2 2 2 3 1 4 3 2
 $ b: num  0.844 0.868 0.519 0.048 0.56 ...
 - attr(*, "createdAt")= POSIXct, format: "2011-03-16 10:42:10.137434"
R> 

and you can then write yourself some custom print() or show() functions that use the attribute. Frank Harrell's rms and its Design predecessor have done something like that for a long time.

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