在R中本地（非全局）设置种子

I'd like to set seeds in R only locally (inside functions), but it seems that R sets seeds not only locally, but also globally. Here's a simple example of what I'm trying (not) to do.

我想在R中仅在本地设置种子（内部函数），但似乎R不仅在本地设置种子，而且在全局设置种子。这是我正在尝试（不）做的一个简单示例。

myfunction <- function () {
  set.seed(2)
}

# now, whenever I run the two commands below I'll get the same answer
myfunction()
runif(1)

So, my questions are: why does R set the seed globally and not only inside my function? And how I can make R to set the seed only inside my function?

所以，我的问题是：为什么R在全局设置种子而不仅仅是在我的函数中？我怎样才能让R只在我的函数中设置种子？

1 个解决方案

#1

Something like this does it for me:

像这样的东西对我来说：

myfunction <- function () {
  old <- .Random.seed
  set.seed(2)
  res <- runif(1)
  .Random.seed <<- old
  res
}

Or perhaps more elegantly:

或者更优雅：

myfunction <- function () {
  old <- .Random.seed
  on.exit( { .Random.seed <<- old } )
  set.seed(2)
  runif(1)
}

For example:

例如：

> myfunction()
[1] 0.1848823
> runif(1)
[1] 0.3472722
> myfunction()
[1] 0.1848823
> runif(1)
[1] 0.4887732

#1