将函数应用于所有参数组合(作为列表输出) [英] Apply a function over all combinations of arguments (output as list)

问题描述

此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，但是当我尝试使用testFunc时收到消息:Error in (function (x, y) : unused arguments (Var1 = "val1", Var2 = 2).

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.

我的期望是得到结果:

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

动机

我来自 Mathematica ，在其上执行此操作非常简单:

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]

我如何在R中做到这一点?

How can I do it in R?

推荐答案

经过几次尝试和错误尝试后，我找到了解决方案.

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

为了使comb_apply正常工作，我需要在使用每个exp值之前先unname.这是代码:

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))会得到所需的结果，而无需更改testFunc.

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

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