在R中向量化'deparse(substitute(d))'吗? [英] Vectorizing 'deparse(substitute(d))' in R?

问题描述

我想知道为什么，当使用以下命令运行以下代码时: bb(d = c(dnorm，dcauchy))我收到一条错误消息: object'c(dnorm，dcauchy)'找不到?

I'm wondering why, when running my below using: bb(d = c(dnorm, dcauchy) ) I get an error saying: object 'c(dnorm, dcauchy)' not found?

P.S..但是，如下所示，该函数对于 bb(d = c(dnorm))来说没有问题.

P.S. But as I show below, the function has no problem with bb(d = c(dnorm)).

bb <- function(d){

 d <- if(is.character(d)) d else deparse(substitute(d))

  h <- numeric(length(d))
for(i in 1:length(d)){
  h[i] <- get(d[i])(1)  ## is there something about `get` that I'm missing?
    }
  h
}
# Two Examples of Use:
bb(d = dnorm)                # Works OK 
bb(d = c(dnorm, dcauchy) )   # Error: object 'c(dnorm, dcauchy)' not found

# But if you run:
bb(d = c("dnorm", "dcauchy"))# Works OK

推荐答案

在将函数直接传递给函数的情况下，尝试使用此替代方法

Try this alternative where you pass the functions directly to your function

bb <- function(d){
  if (!is.list(d)) d <- list(d)
  sapply(d, function(x) x(1))  
}

bb(d = list(dnorm, dcauchy))
bb(d = dnorm)

c()函数是用于组合向量的，它不是一个神奇的数组"函数，也不是任何东西.如果您具有简单原子类型的集合，则可以将它们与 c()相连，但是对于函数之类的更复杂的对象，则需要将它们收集在列表中，而不是向量中.

The c() function is meant to combine vectors, it's not a magic "array" function or anything. If you have collections of simple atomic types, you can join them with c(), but for more complicated objects like functions, you need to collect those in a list, not a vector.

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