将非标准评估参数传递给子集函数 [英] Passing on non-standard evaluation arguments to the subset function

问题描述

我想在另一个函数中使用 subset，但要传递来自顶级函数的非标准评估参数.以下是非工作代码，但概述了这个想法:

I want to use subset within another function but to pass on the non-standard evaluation arguments from the top-level function. The following is non-working code, but outlines the idea:

foo_1 <- function(x, mysubset) 
{
  # some deparse, substitute etc. magic here ??
  subset(x, subset)
}
foo_1(ansombe, x1 > 5)

我希望得到与 subset(ansombe, x1 > 5) 相同的结果.此外，当参数传递到更深层次时，我希望同样的工作，即

I want this to get the same results as for subset(ansombe, x1 > 5). Also, I want the same to work when the argument is passed on to a deeper level, i.e.

foo_2 <- function(x, mysubset) 
{  
  # some deparse, substitute etc. magic here ??
  foo_1(x, mysubset)
}
foo_2(ansombe, x1 > 5)

这里我也想要和上面一样的结果.

Here also I want the same result as above.

到目前为止我尝试过的

我尝试了substitute-deparse、eval-parse的组合，比如

I tried a substitute-deparse, eval-parse combination, like

foo_1 <- function(x, mysubset)
{
  tx <- deparse(substitute(mysubset))
  subset(x, eval(parse(text=tx)))
}
foo_1(anscombe, x1 >5)

这很好，但我现在如何处理 foo_2?

This is fine, but how do I go on for foo_2 now?

此外，我还记得 Thomas Lumley 的格言:

Also, I remember the dictum by Thomas Lumley:

如果答案是 parse() 你通常应该重新思考这个问题.-- Thomas Lumley(R-help，2005 年 2 月)

If the answer is parse() you should usually rethink the question. -- Thomas Lumley (R-help, February 2005)

所以，我想知道是否有比 eval-parse 组合更好的方法.?有什么想法吗?

So, I was wondering if there is a better approach than an eval-parse combination.? Any ideas?

附注.这个问题类似，但不包括更深的嵌套:传递子集参数一个子集函数

PS. This question is similar but does not include the deeper nesting: Pass subset argument through a function to subset

PPS:也许应用 plyr 中的 . 函数很有成效，但我不知道如何...

PPS: Maybe it is fruitful applying the . function from plyr, but I don't know how...

推荐答案

只要你尽可能拖延评估，这样的事情应该可以

As long as you delay the evaulation as long as possible, something like this should work

foo_1 <- function(x, mysubset) 
{
  do.call("subset", list(quote(x), substitute(mysubset)))
}

foo_2 <- function(x, mysubset) 
{  
  do.call("foo_1", list(quote(x), substitute(mysubset)))
}

data(anscombe)
foo_1(anscombe, x1 > 5)    
foo_2(anscombe, x1 > 5)

但是如果你打算用 mysubset 搞砸，你需要更加小心.这将有助于确切地知道你为什么这样做.

but if you plan on mucking about with mysubset you would need to be more careful.It would help to know exactly why you are doing this.

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