R:在循环中定义函数 [英] R: Defining functions within a loop

问题描述

在循环中定义多个功能:

Defining multiple functions in a loop:

par <- 1:2    #parameters for functions
qF <- list()  #list I will write the functions into

for(i in 1:2){
  qF[[i]] <- function(p){qnorm(p, mean = par[i])}
}

我的结果:

>qF
[[1]]
function (p) 
{
qnorm(p, mean = par[i])
}

[[2]]
function (p) 
{
qnorm(p, mean = par[i])
}

功能相同！我想要的结果是:

The functions are the same! What I WANT my result to be:

>qF
[[1]]
function (p) 
{
 qnorm(p, mean = par[1])
}

[[2]]
 function (p) 
{
 qnorm(p, mean = par[2])
}

有什么办法吗?

推荐答案

如果要动态创建函数，则需要每次对 par [i] 进行评估，否则需要对所有 par [i] ，而 i 将是循环结束时的值.

If you want to create the functions dynamically you need for the par[i] to evaluate each time, otherwise all the par[i] will be evaluated when the functions are called, and i will be the value at the end of the loop.

for(i in 1:2){
    qF[[i]] <- local({
        mu <- par[i]
        function(...) { qnorm(..., mean = mu) }   
    })
}

您还可以将变量替换到函数主体中

You could also substitute the variable into the function body

for(i in 1:2){
    qF[[i]] <- eval(substitute(
        function(...) qnorm(..., mean = mu)), list(mu=par[i]))
}

您会看到每个函数环境中的 mu 是什么

And you can see what mu is in each function's environment

sapply(qF, function(f) mget("mu", environment(f)))
# $mu
# [1] 1
# 
# $mu
# [1] 2

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