对所有参数组合应用函数(输出为列表) [英] Apply a function over all combinations of arguments (output as list)

问题描述

这个解决方案几乎是我所需要的，但不适用于我的情况.这是我尝试过的:

This solution is almost what I need, but do not worked to my case. Here is what I have tried:

comb_apply <- function(f,...){
  exp <- expand.grid(...,stringsAsFactors = FALSE)
  apply(exp,1,function(x) do.call(f,x))
}

#--- Testing Code
l1 <- list("val1","val2")
l2 <- list(2,3)

testFunc<-function(x,y){
  list(x,y)
}

#--- Executing Test Code
comb_apply(testFunc,l1,l2)
comb_apply(paste,l1,l2)

它适用于 paste 示例，但我收到消息:Error in (function (x, y) : used arguments (Var1 = "val1", Var2 = 2) 当我尝试我的 testFunc 时.

It works for paste example, but I get the message: Error in (function (x, y) : unused arguments (Var1 = "val1", Var2 = 2) when I try my testFunc.

我的期望是得到这样的结果:

My expectation is to get as result:

list(list("val1",2),list("val1",3),list("val2",2),list("val2",3))

动机

我来自Mathematica，在它上面执行这个操作很简单:

Motivation

I came from Mathematica, on which perform this operation is as simple as:

l1 = {"val1", "val2"}
l2 = {2, 3}
testFunc = {#1, #2} &
Outer[testFunc, l1, l2]

如何在 R 中实现?

推荐答案

经过一些尝试和错误尝试，我找到了解决方案.

After some try and error attempts, I found a solution.

为了使 comb_apply 工作，我需要在使用它之前 unname 每个 exp 值.代码如下:

In order to make comb_apply to work, I needed to unname each exp value before use it. Here is the code:

comb_apply <- function(f,...){
  exp <- expand.grid(...,stringsAsFactors = FALSE)
  apply(exp,1,function(x) do.call(f,unname(x)))
}

现在，执行 str(comb_apply(testFunc,l1,l2)) 我得到了想要的结果，无需更改 testFunc.

Now, executing str(comb_apply(testFunc,l1,l2)) I get the desired result, without change testFunc.

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