如何随时避免（）“通过引用更新”？

I want to convert a numeric variable to POSIXct using anytime. My issue is that anytime(<numeric>) converts the input variable as well - I want to keep it.

我想随时使用数字变量转换为POSIXct。我的问题是，任何时候（）也会转换输入变量 - 我想保留它。

Simple example:

简单的例子：

library(anytime)
t_num <- 1529734500
anytime(t_num)
# [1] "2018-06-23 08:15:00 CEST"
t_num
# [1] "2018-06-23 08:15:00 CEST"

This differs from the 'non-update by reference' behaviour of as.POSIXct in base R:

这与基础R中as.POSIXct的“非按引用更新”行为不同：

t_num <- 1529734500
as.POSIXct(t_num, origin = "1970-01-01")
# [1] "2018-06-23 08:15:00 CEST"
t_num
# 1529734500

Similarly, anydate(<numeric>) also updates by reference:

同样，anydate（）也通过引用更新：

d_num <- 17707
anydate(d_num)
# [1] "2018-06-25"
d_num
# [1] "2018-06-25"

I can't find an explicit description of this behaviour in ?anytime. I could use as.POSIXct as above, but does anyone know how to handle this within anytime?

我无法在任何时间找到这种行为的明确描述。我可以像上面那样使用as.POSIXct，但是有人知道如何在任何时候处理这个吗？

5 个解决方案

#1

You could hack it like this:

你可以像这样破解它：

library(anytime)
t_num <- 1529734500
anytime(t_num+0)
# POSIXct[1:1], format: "2018-06-23 08:15:00"
t_num
# [1] 1529734500

Note that an integer input will be treated differently:

请注意，整数输入将被区别对待：

t_int <- 1529734500L
anytime(t_int)
# POSIXct[1:1], format: "2018-06-23 08:15:00"
t_int
# [1] 1529734500

#2

anytime author here: this is standard R and Rcpp and passing-by-SEXP behaviour: you cannot protect a SEXP being passed from being changed.

任何时候作者：这是标准的R和Rcpp以及路过SEXP的行为：你无法保护被传递的SEXP被改变。

The view that anytime takes is that you are asking for an input to be converted to a POSIXct as that is what anytime does: from char, from int, from factor, from anything. As a POSIXct really is a numeric value (plus a S3 class attribute) this is what you are getting.

任何时候都需要的视图是你要求输入转换为POSIXct，因为这是任何时候的：从char，从int，从factor，从任何东西。由于POSIXct确实是一个数值（加上一个S3类属性），这就是你得到的。

If you do not want this (counter to the design of anytime) you can do what @Moody_Mudskipper and @PKumar showed: used a temporary expression (or variable).

如果您不想这样（与任何时候的设计相反），您可以执行@Moody_Mudskipper和@PKumar所显示的内容：使用临时表达式（或变量）。

(I also think the data.table example is a little unfair as data.table -- just like Rcpp -- is very explicit about taking references where it can. So of course it refers back to the original variable. There are idioms for deep copy if you need them.)

（我也认为data.table示例有点不公平，因为data.table - 就像Rcpp一样 - 非常明确地指出它可以在哪里引用。所以当然它引用了原始变量。有深刻的成语如果你需要，请复制。）

Lastly, an obvious trick is to use format if you just want different display:

最后，一个明显的技巧是使用格式，如果你只是想要不同的显示：

R> d <- data.frame(t_num=1529734500)
R> d[1, "posixct"] <- format(anytime::anytime(d[1, "t_num"]))
R> d
       t_num             posixct
1 1529734500 2018-06-23 01:15:00
R>

That would work the same way in data.table, of course, as the string representation is a type change. Ditto for IDate / ITime.

当然，这将在data.table中以相同的方式工作，因为字符串表示是类型更改。同上IDate / ITime。

Edit: And the development version in the Github repo has had functionality to preserve the incoming argument since June 2017. So the next CRAN version, whenever I will push it, will have it too.

编辑：自2017年6月以来，Github repo中的开发版本具有保留传入参数的功能。因此，下一个CRAN版本，无论何时推送它，都会拥有它。

#3

If you do this, it will work :

如果你这样做，它将工作：

t_num <- 1529734500
anytime(t_num*1)

#> anytime(t_num*1)
#[1] "2018-06-23 06:15:00 UTC"
#> t_num
#[1] 1529734500

#4

Any reason to be married to anytime?

任何时候结婚的理由？

.POSIXct(t_num, tz = 'Europe/Berlin')
# [1] "2018-06-23 08:15:00 CEST"

.POSIXct(x, tz) is a wrapper for structure(x, class = c('POSIXct', 'POSIXt'), tzone = tz) (i.e. you can ignore declaring the origin), and is essentially as.POSIXct.numeric (except the latter is flexible in allowing non-UTC origin dates), look at print(as.POSIXct.numeric).

.POSIXct（x，tz）是结构的包装器（x，class = c（'POSIXct'，'POSIXt'），tzone = tz）（即你可以忽略声明原点），并且基本上是as.POSIXct.numeric （除了后者允许非UTC原始日期灵活），请查看print（as.POSIXct.numeric）。

#5

When I did my homework before posting the question, I checked the open anytime issues. I have now browsed the closed ones as well, where I found exactly the same issue as mine:

当我在发布问题之前完成我的作业时，我随时检查了问题。我现在也浏览了封闭的那些，在那里我找到了和我一样的问题：

anytime is overwriting inputs

随时覆盖输入

There the package author writes:

包裹作者写道：

I presume because as.POSIXct() leaves its input alone, we should too?

我认为因为as.POSIXct（）单独留下输入，我们也应该这样做？

So from anytime version 0.3.1 (unreleased):

所以从任何时候版本0.3.1（未发布）：

Numeric input is now preserved rather than silently cast to the return object type

现在保留数字输入而不是静默转换为返回对象类型

Thus, one answer to my question is: "wait for 0.3.1"*.

因此，我的问题的一个答案是：“等待0.3.1”*。

When 0.3.1 is released, the behaviour of anytime(<numeric>) will agree with anytime(<non-numeric>) and as.POSIXct(<numeric>), and work-arounds not needed.

当0.3.1被释放时，任何时候（）的行为将随时（ <非数字> ）和as.POSIXct（ <数字> ）一致，并且不需要解决方法。

*Didn't have to wait too long: 0.3.1 is now released: "Numeric input is now preserved rather than silently cast to the return object type"

*不必等待太久：0.3.1现在已经发布：“现在保留数字输入而不是静默地转换为返回对象类型”

#1