你可以在 R 中传递引用吗? [英] Can you pass-by-reference in R?

问题描述

你能用R"传递引用吗?例如，在以下代码中:

Can you pass by reference with "R" ? for example, in the following code:

setClass("MyClass",
    representation(
    name="character"
    ))


instance1 <-new("MyClass",name="Hello1")
instance2 <-new("MyClass",name="Hello2")

array = c(instance1,instance2)

instance1
array

instance1@name="World!"

instance1
array

输出是

> instance1
An object of class "MyClass"
Slot "name":
[1] "World!"

> array
[[1]]
An object of class "MyClass"
Slot "name":
[1] "Hello1"


[[2]]
An object of class "MyClass"
Slot "name":
[1] "Hello2"

但我希望它是

> instance1
An object of class "MyClass"
Slot "name":
[1] "World!"

> array
[[1]]
An object of class "MyClass"
Slot "name":
[1] "World!"


[[2]]
An object of class "MyClass"
Slot "name":
[1] "Hello2"

有可能吗?

推荐答案

否.

赋值语句中的对象是不可变的.R 将复制对象而不是只是引用.

Objects in assignment statements are immutable. R will copy the object not just the reference.

> v = matrix(1:12, nrow=4)
> v
           [,1] [,2] [,3]
     [1,]    1    5    9
     [2,]    2    6   10
     [3,]    3    7   11
     [4,]    4    8   12
> v1 = v
> v1[,1]     # fetch the first column 
     [1] 1 2 3 4

(附带条件:上述陈述适用于 R 原语，例如向量、矩阵)，也适用于函数；我不能肯定它是否适用于所有 R 对象——只是其中的大部分，以及绝大多数最常用的对象.)

(proviso: the statement above is true for R primitives, e.g., vectors, matrices), and also for functions; I cannot say for certain whether it's true for all R objects--just most of them, as well as the vast majority of the ones most often used.)

如果您不喜欢这种行为，您可以在 R 包的帮助下选择退出.例如，有一个名为 R.oo 的 R 包，它允许您模仿传递引用行为；R.oo 可在 CRAN 上使用.

If you don't like this behavior you can opt out of it with the help from an R Package. E.g., there is an R Package called R.oo that allows you to mimic pass-by-reference behavior; R.oo is available on CRAN.

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